On a Plesk for Windows server, the Plesk interface and websites are not accessible:
HTTP Error 503. The service is unavailable.
The following error is found in Event Viewer > Windows Logs > Application:
The Module DLL C:WindowsSystem32inetsrvpleskurlprotection.dll failed to load. The data is the error
Windows Server OS was upgraded between major releases (for example, from 2016 to 2019), which is not supported by Plesk.