"HTTP Error 503. The service is unavailable." appears when trying to open the DocuWare WebClient. After Upgrading Windows to version 1709, the DocuWare Application Pools don't start anymore and the Windows Event Viewer is displaying: "The configuration file cannot be read. Occurred while attempting to read configuration data from file '\\?\<EMPTY>', line number '0' The data field contains the error code" - Event 2307

This is caused by a bug in the Windows 10 Fall Creators Update, more information can be found here:

 To resolve this issue, please follow these instructions:

  1. Open Windows Powershell as administrator
  2. Run: Stop-Service -Force WAS
  3. Run: Remove-Item -Recurse -Force C:\inetpub\temp\appPools\*
    Important: If this gives you an error, delete all folders found inside of "C:\inetpub\temp\appPools\" manually and continue with step 4 afterwards
  4. Run: Start-Service W3SVC
  5. The DocuWare Application Pools are starting again and the HTTP Error 503 disappears

Note: There is no need to start the Service "WAS" again because Step 4 is doing that already.