A 500 Internal Server Error can have several causes. Follow these steps to diagnose and resolve it: 1. Check the server logsFirst, review all available logs on the server for detailed error information: PHP error logApache (or the web server you are using) error log The logs usually contain the exact reason for the failure. 2. Website builder doesn't meet all the requirementsMake sure that your on-premises builder installation meets all the requirements listed on this page. 3. PHP version was changed on hostingNote that there are different archives for the on-premises builder installation depending on the PHP version. Changing the PHP version on your hosting can cause the website builder to stop working. To resolve this issue, either: Perform a manual builder update by choosing the archive that matches your current PHP version.Switch back to the previous PHP version for the website builder. 4. Error after a manual builder updateIf the error started right after a manual update of the builder, you may have selected an update archive for the wrong PHP version.To fix this, perform the manual update again and choose the archive that matches your server’s PHP version. 5. Unsupported Apache directivesSome directives in the builder's .htaccess file may not be supported because the required Apache modules are not enabled or the server lacks the necessary permissions.Check which directives are causing the problem (they are usually listed in the server error log) and either enable the missing modules or adjust the .htaccess file accordingly. Note: If your on-premises builder installation meets all the requirements but the error persists, the issue falls outside the scope of Site.pro support. In this case, please have your server administrators investigate the issue.