Plesk and websites are not accessible: 500.19 - Internal server error - Module DynamicCompressionModule

Symptoms

• Plesk and websites are not accessible with the error:

  PLESK_INFO: 500 Internal Server error

• After temporary renaming web.config file in %plesk_dir%admin\htdocs, Plesk starts to load with this error message locally on the server:

• PLESK_INFO: HTTP Error 500.19 - Internal Server Error
  The requested page cannot be accessed because the related configuration data for the page is invalid.
  
  Detailed Error Information:
  Module DynamicCompressionModule
  ...
  Error Code 0x8007007e

  Note: Error code can also be 0x80070005.

• The following error message may appear in %plesk_dir%admin\logs\php_error:

  CONFIG_TEXT: ERR [panel] Could not ping database connection: Unable to get PSADb administrator password: The system cannot find the file specified. (Error code 2) at Unable to connect to pipe ...

Cause

The file %windir%\system32\inetsrv\config\ApplicationHost.config refers to a compression scheme that is not properly configured.

Resolution

1. Connect to your Plesk server via RDP.
2. Start a Command Prompt as an Administrator.

3. Run the following command to locate the module reference that is invalid:

   C:\> %windir%\system32\inetsrv\appcmd.exe list config -section:system.webServer/httpCompression | findstr "dll"

   In the example below, the faulty module is "xpress" ("br" and "gzip" are default):

   MYSQL_WIN: <scheme name="br" dll="%ProgramFiles%\IIS\IIS Compression\iisbrotli.dll" />
   <scheme name="gzip" dll="%ProgramFiles%\IIS\IIS Compression\iiszlib.dll" />
   <scheme name="xpress" doStaticCompression="false" doDynamicCompression="true" dll="C:\Program Files\WSUS\Services\WebServices\suscomp.dll" staticCompressionLevel="10" dynamicCompressionLevel="0" />

4. Create a backup file of IIS configuration:

   C:\> %windir%\system32\inetsrv\appcmd.exe add backup BeforeEditBackup

5. Remove the faulty compression scheme from IIS configuration (replace xpress in the command below, if the name is different):

   C:\> %windir%\system32\inetsrv\appcmd.exe set config -section:system.webServer/httpCompression /-[name='xpress']

6. Open the file %windir%\system32\inetsrv\config\ApplicationHost.config in a text editor and search for the line with the scheme name:

   CONFIG_TEXT: xpress scheme <scheme name="xpress" doStaticCompression=... />

   If it exists, remove the line and save the changes.

7. Restart IIS:

   C:\> iisreset

   Note: Restore web.config file in %plesk_dir%admin\htdocs, if it has been renamed.