Most often the problem is related to the fact that website builder that you use is running under HTTP protocol whereas DirectAdmin is running under HTTPS protocol. Since website builder in DirectAdmin Evolution skin is tried to be open in an iframe, it is blocked due to browser CORS policy and the progress is stuck on loading step. To fix this issue you can either enable HTTPS protocol for website builder (for more details on how to do this, please refer to this FAQ: Run website builder under HTTPS protocol) or update Site.pro plugin on DirectAdmin by our DirectAdmin plugin documentation.