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If you migrate one or more websites/accounts to another server then some changes might be needed in builder for a successful migration.
There can be some cases when actions might be required. Note. Use these recommendations only if domains of websites are not changed.

1. Website/account is moved from one server to another where both servers use the same builder brands. In this case no actions are required.

2. Website/account is moved from one server to another and servers use different builder brands. In this case action is required before website migration. Note that it does not depend on who belongs server where website is about to be migrated - whether it belongs to you or to another hosting company. You will need to migrate website from old builder (used on old server) to new builder (used on new server):
1) Open builder for migrating website on old Hosting Panel. Hover on Publish icon and press "Backup/Restore" item;
2) Download backup;
3) Migrate website/account;
3) Open builder for migrated website on new Hosting Panel. Select Backup/Restore, restore it;
4) Publish the website.
Note that server where website was migrated also must be licensed on Site.pro (must have license with new server IP).

Mass website/account migration
If you want to migrate many websites from one server to another at once and servers use different builder brands then please contact us in tickets and we will give you instructions.

Documentation page — https://site.pro/docs/plugins/

Documentation page — https://site.pro/docs/builder/

1. Client accidentally pressed "Reset" or "Change template" button. Check if your client has manual or automatic (available for enterprise) backup enabled;
2. Client closed website builder without pressing "Save draft" after creating a website;

1. Make sure you are viewing the same site version (Wide, Desktop, Tablet, Phone) both in builder and on published website;
2. Clear Internet browser cache.

The Site.pro website builder accessible only via your Hosting Panel or Site.pro account.

The reason is that the user migrated to another account in hosting panel and the username was changed. The builder thinks it is a different user and doesn't open the builder. In this case inform us and we will update the user in our system.

1. Passive mode for FTP is not enabled on your server or too few passive FTP ports are opened. Please enable it and try again. Make sure that all used passive FTP ports are white listed in server firewall.
2. Make sure that there is enough simultaneous FTP connections from one IP allowed on server.

For On-Premises brand only:
3. To fix issue you can try to increase limit number of FTP connection retries in builder configuration:

• open file "config.json" located in builder base folder
• add parameter "ftpConnectionRetriesAllowed" (or edit if it already exists), e.g:
  "ftpConnectionRetriesAllowed": 20,
• save "config.json" file

Open builder again and re-publish website to check if the error is gone.

Check values of PHP parameters "post_max_size" and "upload_max_filesize". Recommended values are 128M for both. If they are less, uploading images/files to builder may not work properly. Increase them (Apache server restart will be needed) and try to upload an image/file again.

1. The problem usually occurs due to firewall on your server which blocks connections from builder server on port 21.

For Cloud brand:
Allow connections from the following IPs on your server on ports 21, 80 and all ports which you have configured for passive FTP connections:
- 3.123.96.42
- 185.25.50.34
- 18.196.241.217
- 104.196.132.63
- 104.199.204.141
- 188.225.9.184
- 52.67.222.115
All these IPs can be used for builder opening.
To allow IPs in firewall please execute the following command:
iptables -A INPUT -p tcp -s 3.123.96.42,185.25.50.34,18.196.241.217,104.196.132.63,104.199.204.141,188.225.9.184,52.67.222.115 -j ACCEPT
Note: the command can vary depending on firewall service you use on your server.

For everyone:
Another possible reason for this issue can be in the fact that you do not have any FTP service running on your hosting server. This can be checked by running service status:
service proftpd status
service pure-ftpd status
If none of them return active (green) status then you need to enable the one which you have on your server installed.
Note: On Cpanel server you can enable FTP service per WHM "FTP Server Selection" menu.

Check if you added "dot" at the end of builder domain in DNS record (it has to be not "builder.domain.com" but "builder.domain.com."). If you added it correctly try to wait for some time for a domain to propagate over the internet, it may take several hours.

1. The problem may be caused by FTP server accepting only SSL connections.
Only for Cloud brand:
We can add your IP address to the exception list so that FTPS publication is applied. If you agree, please, let us know by creating ticket. As a temporary solution you can disable forced SSL connections on your server.

2. The problem may be caused by FTP server using custom port (not the default one - 21).
In this case contact us in the ticket and specify port used by your FTP server. We will configure it for your builder. Alternatively, you can configure it in your brand in "Configuration" section.

Please try to enable PHP extension "exif" and try to upload .png image again.

After license upgrade, Site.pro badge is still displayed on websites. Your logo is starting to be displayed only on newly created websites.

Choose the old one first and write to support@site.pro or create a ticket to migrate your clients to a new server.

If you want to have website builder and mail server on the same domain, you need to add MX records to that domain (pointing to your mail server IP address).

One of the reasons of this error can be the fact that one of your customers (or more) are using dedicated IP for his account which is not listed among your license(s). You need to add such IP(s) to the license as well or move such customers to a shared hosting IP.

When using "Custom (API)" method:
If you use API in order to open builder then this error is usually caused by the fact that the license cannot be detected by parameters of API call. The license is searched by 3 different IPs in specified order:

1. by FTP host parameter "apiUrl" which you pass among parameters list in API call (only if the parameter "apiUrl" has format of IP address and not of a domain);
2. by IP address of parameter "domain" which you pass among parameters list in API call (if it is resolved).
3. by outgoing (external) IP address of server which calls builder API;

If at least one of these cases match IP(s) in your Site.pro license(s) then the license is considered validated and API returns a valid URL to builder. Otherwise the error "License is required" is thrown.
So to fix this issue just make sure that during API call in your case the IP of one of specified 3 cases matches IP(s) in your license.

For On-Premises brand only:
Go to Site.pro licenses page, open On-Premises brand and click "Apply" button. If this action results in error then it means that license synchronization fails and cannot be synchronized with your builder. If error message do not help to fix this issue by yourself then create ticket in support system and describe this problem.

If you want to run builder domain under HTTPS protocol you need to do the following steps:

For Cloud brand:
Create a ticket and inform us that you want to have builder domain running with https protocol. We connect Let's Encrypt free SSL certificates for Premium-brand owners. If you have your own certificate files then attach them to the ticket with a ZIP file.
Please note, that Free SSL can be enabled for customers who have Trusted Partner status.

For On-Premises brand:
1. Open your On-Premises brand and change builder domain by adding "https://" at the beginning of it (e.x. "builder.yourdomain.com" -> "https://builder.yourdomain.com")
2. Open file "config.json" in your builder web root directory and update parameter "siteProApiUrl" by changing "http://" part to "https://"
3. Go to Site.pro licenses page, open On-Premises brand and click "Apply" button.

Subdomain should be created in the hosting panel, then your clients will have access to the builder for a new subdomain via their hosting panel.

If the client ruined his website only in site builder whereas the published version is still correct, then inform us about it in the ticket and our team will restore client's website in the editor from published version.

If the client published ruined website to hosting, then the only way to restore the correct website version - is to restore account backup on used hosting control panel (cPanel, Plesk, etc..). After you get correct published website version then inform us about it in the ticket and our team will restore website in the editor.

For On-Premises brand only:
Provide us FTP or any other access to published website files, so that we could use them for website restoring in builder.

Possibly the license synchronization with your builder fails when you click "Save" button in the license.
To fix this problem use these methods:
Method 1:
Check whether PHP parameter "allow_url_fopen" is ON in builder hosting PHP configuration.
1. Set this parameter to ON and restart server.
2. Save On-Premises brand and check if builder logo appeared (we recommend to check logo in new builder session, for example in another browser).
Method 2:
Check if API username and password which you entered during builder installation are correct.
1. Open builder file "config.json" located in builder web root folder.
2. Locate parameters "apiUsername" and "apiPassword".
3. Make sure they are the same as specified in On-Premises brand.
4. Fix them if needed (if password in the license contains symbols "/" please replace it with "\/" in "config.json" file) and save the file.
5. Save On-Premises brand and check if builder logo appeared.
Method 3:
Check if firewall of your builder server does not block site.pro server.
We recommend to white-list site.pro IPs from which license synchronization can be made:
- 3.123.96.42
- 185.25.50.34
- 18.196.241.217
- 104.196.132.63
- 104.199.204.141
- 188.225.9.184
- 52.67.222.115
Method 4:
If method 1 and method 2 did not solve the problem:
1. Open file ".htaccess" located in builder web root folder.
2. Comment line below:
RewriteRule ^(.*)$ index.php [L,QSA]
3. Uncomment line:
#RewriteRule ^(.*)$ index.php?HTTP_AUTHORIZATION=%{HTTP:Authorization} [L,QSA]
4. Save file.
5. Open file "config.json".
6. Add parameter "keepHtaccess": true somewhere in the middle and save the file.
7. Save On-Premises brand and check if builder logo appeared.

Builder requires FTP passive mode enabled on your server to be able to publish websites.
If you server is behind NAT then make sure that FTP passive mode is properly configured:
use extra option "MasqueradeAddress" (for ProFTPD) or "ForcePassiveIP" (for Pure-ftpd) and specify your external IP address.

To solve this problem please take the following steps:
1. Open builder in Chrome or Firefox browser
2. Open developer tools in browser (key F12)
3. Switch to "Network" tab
4. Click on "Save" button in builder
5. Click on appeared request line (it should begin with "?sess=")
6. Switch to "Response" tab
7. Copy text you see in this tab
8. Create ticket on site.pro and tell us about "server error" and paste copied text. Our developers will fix this problem.
9. Thank you and excuse us for inconvenience.

To solve this problem please take the following steps:
1. Open builder in Chrome or Firefox browser
2. Open developer tools in browser (key F12)
3. Switch to "Network" tab
4. Click on "Save" button in builder
5. Click on appeared request line (it should begin with "?sess=")
6. Switch to "Response" tab
7. Copy text you see in this tab
8. Create ticket on site.pro and tell us about "error loading page" and paste copied text. Our developers will fix this problem.
9. Thank you and excuse us for inconvenience.

In order to fix this problem just create API key from Google by going to this link https://developers.google.com/fonts/docs/developer_api and put key in file "config.json" located in builder web root folder - you need to set it to parameter "googleFontsApiKey".

Note. Most probably Google Maps widget also does not work in your builder. To make it working do the same as for Google Fonts but use this link for key creation https://developers.google.com/maps/documentation/javascript/get-api-key and parameter "googleMapsApiKey" in file "config.json".

The problem may occur when you are using field Form will be sent from this Email in form configuration in builder. For example you use address in this field example@mysite.com. Then mails may not be received on your email account due to the fact that domain mysite.com does not have DNS record of type SPF (for more details please see https://en.wikipedia.org/wiki/Sender_Policy_Framework). Due to this mails can be blocked by mail servers. If you are an owner of domain "mysite.com" you need to add SPF record in DNS configuration of your domain.

When you do not have field "Form will be sent from this Email" filled in then the address no-reply@mysite.com is used (where "mysite.com" is replaced with your website domain name). In this case the reason of not receiving mails is the same as described above.

The problem occurs due to the fact that different devices and different browsers can render text a little differently what can have impact on text height (and as a result - text overlapping each other). To fix this problem you can follow these recommendations:
1. Do not use 0 value for Line height option for fonts in Styles menu. Here "0" means "normal" and it can be interpreted differently on different devices and browsers. Set some value which would be similar as it was with "0" (e.g. if you use font size "16" then line height can be around "19-20" what would make text look more or less the same as with value "0").
2. Do not forget to set style to text in Text widget. Double-click to edit text, select some text and look at what is chosen at left dropdown of text editor. It there is "Style" - it means that no style is set for selected text. Due to this any font can be used on published website depending on device and browser.
3. Avoid creating very huge Text widgets (containing a lot of text). If you have one just try to separate it to multiple Text widgets. Despite the fact that you did recommendation (1) and (2) some devices and browsers can continue render text a little differently. Most probably you will not see any difference in small texts but when there are huge text blocks on site the problem can occur.
4. Use Google fonts which are supported on majority of devices. Some default fonts may not be supported on different devices. They automatically replace font with a different one when you view site (it can be very similar) which can also contain small difference.

If you migrate your clients to another server and IP of new server changes then you need to update IP in your license on Site.pro licenses page from old value to new value after migration. The plugin re-installation or other actions are not needed.

Note for On-Premises Brand: The IP update on licenses page is needed only if you migrate hosting server with clients. In case if only builder server is moved then no actions are needed at all. There is no need in having IP for builder server on licenses page if that server is used only as builder and not as hosting server with clients.

If error "Server error (403)" is thrown during saving draft/publishing or other actions in builder then it can happen due to the following reasons:

1. Your builder session has expired. The session in builder should never expire when you edit website. However there are few cases when it can happen:

• someone else opened builder with your website from your account of hosting control panel. This action leads to your session expiration and new session establishing for another person.
• you opened builder one more time for the same website in another browser or in incognito window. This action leads to session expiration of first window and new session establishing for new window. To avoid this in the future we recommend you to have only one builder window opened at one time.
• you left builder window opened for a long time and your computer went to sleep or darkened screen. This can lead to limited browser activity for opened windows and prevent builder from refreshing session.

Unfortunately if session expires it means that all your changes made after last draft saving in builder will be lost. To continue editing website in builder you need to open builder again from hosting control panel.

2. (Only for On-Premises brand) Builder is facing temporary server problems. During saving draft/publishing website a big set of data is sent to server. Sometimes servers can have some active POST filters which scans all data by some criteria(s) and can block request to server if needed.
To fix this issue contact your hosting provider (or site builder administrator) and tell about this problem.

These errors can be thrown during publication if nginx server is used for builder. Usually the reason of them is script timeout. Increase timeout for nginx script execution (parameter fastcgi_read_timeout), restart nginx server and check if error is gone.

If nginx server is used as proxy server for Apache then increasing these parameters in nginx configuration may help to solve the problem:
proxy_connect_timeout, proxy_send_timeout, proxy_read_timeout, send_timeout

For Cloud brand: Unfortunately the limit of restorable backup files cannot be changed if you use premium brand. For backup file restoration which exceeds builder limit please create ticket on tickets page and specify us website domain and external link to backup file which you want to restore. Our team will restore it and we will notify you.

For On-Premises brand: The builder limit parameter directly depends on PHP parameters post_max_size and upload_max_filesize on server where builder is installed. So the limit is a smaller value of these 2 parameters. Just update values of these parameters in PHP settings and the limit in builder will automatically change.

Important! If you have your on-premises builder domain configured with CloudFlare (or use different proxy service), then specified PHP parameters must also be raised in that service.

Most probably you installed site builder plugin on your hosting panel before you set plugin icon and title in your brand on Site.pro licenses page. In order to update icon and title on your hosting panel just make plugin re-installation by instruction which you can find on this page.

When you get this error when sending mail from your site then it usually means one of these:

• SMTP data is incorrect (double-check username and password, make sure that you specified correct host and port).
• Firewall on your hosting server blocks outgoing connections from specified SMTP host and/or port. Contact your hosting support and describe this problem to fix the issue.
• Specified SMTP host (in case if it is a domain — not IP) is not resolved on your hosting server or resolved to a wrong IP address. Contact your hosting support and describe this problem to fix the issue.

For more details on this issue please refer this page.

The publication process consists of the following steps:

1. Builder generates final site files and tries to publish only those which were modified after previous publication.
2. After publication of changes builder tries to call script on published site and check in this way whether all required site files exist on the hosting.
3. If (2) ends with "false" response (that is eventually not all files exist on hosting) then builder re-publishes all site files.

Sometimes builder stuck on step (2) (or takes much time — 1-2 minutes) since connection to the end site can be problematic. Sometimes firewall on hosting server blocks builder IP on port 80. Due to this connection hangs until timeout is reached and builder tries different IP to connect.
To avoid such problem make sure that builder IP is white listed on port 80 in hosting server firewall.

Why the restriction exists:
1. Hosting companies are asking us to protect them from losing customers, as people can switch to a cheaper hosting provider after a website is created. But when websites stop working (on another provider) customer usually returns back to the old provider;
2. This model fits all servers network architectures;
3. There is no other way to control the number of websites as hosting providers constantly migrate among servers.

When website domain is changed then it is no longer opened in site builder. Most probably you will see initial page offering you to choose template. This happens due to the fact that website identification is made by website domain. If it is changed then site builder sees that website as new and offers you to choose template.
To get back your website and make it working under a new domain please follow instruction below.

For Cloud brand:
Contact us in support system by creating new ticket and provide us old and new domain names. Our team will update domain in site builder and the website will become editable again.

For On-Premises brand:
Use builder API to rename website in your site builder installation.

Only for Cloud brand:
If you want to migrate to another cloud builder server (e.g. from EU to US) then create new ticket in support system and tell us about migration. In the ticket please specify us cloud builder server you want to migrate to. We will provide you with further instructions.

If you get error "Can't find destination folder" during publication then it means that builder could not find folder on your hosting where to publish website files.

When using "Custom (API)" method:
To fix this error you need to review parameters which you pass to builder API when creating session for a customer. The parameter which is responsible for this error is uploadDir. Make sure that it has a value of relative directory on your hosting in respect to FTP account which you pass along with other parameters.
For example if the customer "A" on your server has web folder "/home/user_A/public_html" and FTP account (parameters "username", "password", "apiUrl") which you pass to builder API points to directory "/home/user_A" then the parameter "uploadDir" must have value "public_html".

When using pre-defined hosting panel (cPanel, Plesk, etc.):
The builder plugin on hosting control panel should automatically detect FTP account and customer's web folder where to publish website. However in rare cases API of hosting panels can return wrong FTP folder and as a result the publication ends with the error. In this case you may try to reset FTP account for the customer on your hosting control panel. If this does not help then open a ticket in support system and describe the problem - our technicians will suggest the solution individually.

The publication process is the process which starts when the client presses button "Publish" in builder toolbar. The process can be divided into several parts which are executed one after another in specified order:

1. saving draft — this step saves website draft — the same action which is triggered when pressing button "Save Draft". This step takes <1 second; when it completes the state "preparing..." is displayed
2. website generation — during this step builder generates final website files which will be published to client's hosting. They consist mostly of .php, .js, .css and different media files. During this step the state "building website..." is displayed.
3. connection to hosting FTP server — this is the 1st step of deploying part. The builder tries to establish FTP connection with hosting server where it will publish website. The connection is made with 3 different IPs in specified order until it finally connects (when it connects with some of them it does not try the rest):
   1. IP address which was passed by hosting control panel API to builder plugin when builder was opened (in case if "Custom (API)" is used then it is defined by parameter "apiUrl");
   2. IP address of domain which was opened (in case if "Custom (API)" is used then it is defined by parameter "baseDomain" [or "domain" if "baseDomain" is not provided]);
   3. remote IP address of server which made API call to builder during opening;
   During this step the state "connecting..." is displayed.
4. logging to hosting FTP account — this is the 2nd step of deploying part. After successful connection to FTP server builder tries to log in with username and password of FTP account. Builder gets FTP data from builder plugin on hosting control panel (API) (in case if "Custom (API)" is used then FTP details are defined by parameters "username" and "password").
5. files uploading — this is the 3rd step of deploying part. During this step website files are uploaded to hosting. Note that only changed files are uploaded from last publication. This is usually the longest part. It can take from few seconds to few minutes (depending on website size and connection speed between builder and hosting servers).
6. verification — this is the 4th step of deploying part. After successfully uploaded website files (only changed) to hosting then builder makes verification whose purpose is to check if all required website files are on hosting and they are all correct. During this step builder connects to website hosting on port 80 or 443. The connection is made also with different IPs in the same order and same IPs as during builder connection to FTP server with one difference — firstly it tries IP address which could successful establish connection to FTP server. During this step the state "verifying..." is displayed.
7. files re-uploading (full) (optional) — this step is taken only in the case if verification returned negative result, that is some website file on hosting was removed or changed since last publication. During files re-uploading the connection to FTP is made again as described in step (3). When the uploading ends then no second verification is made.

Note that practically all these steps are executed quite quickly and usually client does not see them all in publication process bar.

Builder plugin is a module for hosting control panel (cPanel, Plesk, etc.) which is installed on panel and displayed for end clients as an extra button among other buttons. The builder button can be customized with your own icon and title.

The builder plugin works as a gateway from panel to site builder. Plugin purpose is to retrieve all required information of client account from hosting control panel (using internal API) and pass it to site builder. The required information includes:

• client's FTP account data (username and password)
• client's hosting IP address (which is used as FTP host in builder during publication)
• client's domain
• client's account package (if supported by panel).

After plugin collects information it calls builder via API and pass information for it. Builder checks the license of your hosting server and determines whether to let you in or not. If the license is verified then builder API returns URL otherwise it returns error message. In case if plugin gets URL from builder it redirects the client by this URL to builder where client can construct his website. If the license verification fails then builder returns error message "License is required" meaning that the license could not be detected by API call and provided parameters (check how to fix this error).

The communication between builder plugin and builder is made via HTTP port 80 or 443 depending what protocol builder uses. In case if you use Cloud builder then 443 port is always used. If you use On-Premises builder then it depends on what protocol your builder is running on.

When the client opens builder for the first time then builder suggests to choose a template first before starting constructing website. During website construction all website data is saved in special ".dat" files in builder storage and all media files which client uploads are also stored in builder. Note that during website construction in builder no changes are made on client's hosting. Changes are applied only when client presses button "Publish" in builder toolbar — then builder generates real website files (consisting of .php, .js, .css and other files) and publishes them to client's hosting via FTP connection (see how publication works in more details).
When the client next time opens builder then builder finds his ".dat" files and loads them instead of offering to choose template anew. Note that when client opens builder then builder does not download client's current website files from hosting — builder has all website data in his own storage.

The identification of website in builder is made only by domain. It means that the client can have multiple websites in his account (addon domains, sub-domains) and construct websites in builder separately for all of them. If client's domain is renamed further then it also must be renamed in builder separately. Otherwise the client will be offered to choose template anew as if the website was opened for the first time.

If you have your own hosting control system for your customers and do not use predefined hosting control panel which we support then you can also use site builder by implementing your own plugin using builder API method to create session.

Site.pro builder Store module supports mail notifications. Mail notifications can be sent both for the merchant and for the customer. There are 2 cases when notifications are sent: when the order is submitted and when the payment for order is received.

In order to configure mail notifications for yourself (merchant) add email address in builder Store properties → Settings tab → Contact Form block. Click "pencil" icon in contact form block and switch to "E-mail settings" tab. Type your email address in field "Form will be sent to this E-mail" where you want to receive mail notifications. You can also configure SMTP options in the "SMTP" tab.

Customers will get mail notifications to email address which they enter in Billing Information block. Note that Billing and shipping blocks can be disabled for customers in Store Cart module. To check if it is not disabled ensure that the option "Require Billing/Shipping Information" is enabled in Store Cart module.

Why do I not receive mail notifications even after adding email address in Store configuration?
Despite you added email address in "Contact Form" block settings there can be cases when mail notifications are not delivered. The usual reason for that is the absence of SPF record of your website domain. Please check this page for more details about this problem.

If you have one or more plugins disabled in builder toolbar (e.g. Commerce or other) then there can be 2 reasons for this:

1. you have this plugin disabled per plans configuration. To check this:
   • open Site.pro licenses page
   • click on your brand to open it
   • to go item "Edit Plans"
   • check what plugins you have disabled for each builder plan and consider enabling some of them if needed.
2. you specified wrong hosting plan names in field "Relate with these hosting plans" and as a result the wrong builder plan is loaded for the customer. In this case check real hosting plan names from your end and fix their values on Site.pro if needed.

All orders are saved in published website in one of the data file. The only reason of missing orders may be related to file deletion (possibly you deleted website files and then re-published website).

The older file having all orders may be returned by restoring published website backup from hosting control panel of earlier version. After restoring the client should check in builder if earlier orders appeared. However note that website backup restoring on hosting will restore the whole earlier website version. So to make it up-to-date again just re-publish website in builder (builder will have up-to-date version). The re-publication will not delete restored orders.

If you see this message on published website then it means that your used API key lacks some requirements on Google console account. In order to see details of the problem open Developer console in browser on your website page with Google map (usually key F12) and switch to tab "Console". There you should see red error message from Google with problem details. Follow specified recommendations to fix the problem.

Some builder elements, like Store, Store Cart, Blog and others may have their own built-in words and buttons with native words. For example Store has buttons like "Add to Cart" or texts like "Price", "Category", etc. These values cannot be changed, and sometimes they are published in English language rather than the desired language.

The language of these words depend on website language. The website language is determined in 2 ways:

• When using Flags element — then your website is considered multilingual and built-in words on website will be translated on published website to a language the website is currently opened on.
• When using no Flags element — then website language is determined by site builder language during website publication. So if you do not use Flags element and want built-in words to be translated the desired language, then make sure that you have builder switched to that language before publishing website.

In rare cases the publication of website can take a lot of time and end with error "Operation timedout, try again later" (in this case publication may take up to 2 hours). Unfortunately this error does not provide any details, but the sure thing is that something broke publication process and it just stopped in a background leaving the client to wait without any progress.

The main reason of this error is a lack of RAM on server which is dedicated for PHP processes for builder. In Cloud brand builders this value is configured quite big, but in rare cases such problem still can appear. However in On-Premises brand builders the limit of RAM can be too small what can cause this problem more often. Note that, despite the fact the recommended value for builder installation is 256M, sometimes it may not be enough.

To fix the problem you may try the following:
Only for On-Premises builder:
1. Increase limit of memory dedicated for PHP (parameter "memory_limit"). Unfortunately it is not known what value the parameter must be increased to, because it primarily depends on pages count of published website. Roughly speaking, for ~100 pages of website the value must be not less than 256M.
For Cloud and On-Premises builder:
2. (only for builder v3) The combination of many pages on website (more than 100) and enabled Auto Layout option may require much more RAM for website generation during publication. If there are much more pages than 100 then we recommend you to turn off option "Auto Layout" and use 4 standard methods (Wide, Desktop, Tablet, Phone).
3. During long website creation/maintenance there can be many unneeded (outdated) pages left in builder with time. Remove all unused pages and try to publish website again.