Website hosted in Plesk shows 500 error: Provider cannot be found. It may not be properly installed.

Symptoms

• Website hosted on Plesk does not work:

  external Server Error 500

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  The 'Microsoft.Jet.OLEDB.4.0' provider is not registered on the local machine.

• While accessing website directly from the server shows:

  Could not load file or assembly 'XXXXX' or one of its dependencies

  ---

  Assembly binding logging is turned OFF

• Enabled Failed request tracing shows the following:
  

  Provider cannot be found. It may not be properly installed.

  ModuleName IsapiModule
  Notification EXECUTE_REQUEST_HANDLER
  HttpStatus 500
  HttpReason external Server Error

  ---

  The requested resource is in use (0x800700aa)

Cause

32-bit application mode is disabled in application pool settings.

Resolution

1. Log in to Plesk
2. Go to Domains > example.com > Dedicated IIS Application Pool for Website
3. Check the checkbox Enable 32-bit applications and click OK