Plesk and sites are not accessible: 503 The Module DLL C:WindowsSystem32inetsrvpleskurlprotection.dll failed to load. The data is the error

Symptoms

• On a Plesk for Windows server, the Plesk interface and websites are not accessible:

  Service Unavailable
  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

Cause

Windows Server OS was upgraded between major releases (for example, from 2016 to 2019), which is not supported by Plesk.

Resolution

Deploy a new clean Plesk for Windows server and migrate to it using Plesk Migrator.