Plesk shows HTTP Error 503. The service is unavailable: A listener channel for protocol ‘http’ in worker process serving application pool ‘PleskControlPanel’ reported a listener channel failure

Symptoms

• Unable to access Plesk GUI, the following error is shown:

  HTTP Error 503. The service is unavailable.

• Plesk uses IIS as a Web server. IIS Advanced Logging or IIS Mod-Rewrite is installed on the server. Going to IIS > Sites > PleskControlPanel > ISAPI Filters > There are third-party ISAPI filters registered as shown in the following screenshot:

  

• Plesk Default application pool crashes several seconds after it has been restarted and the following error is shown in Event viewer:

  Log Name: System
   Source: Microsoft-Windows-WAS
   Date: 9/29/2009 1:02:52 PM
   Event ID: 5139
   Task Category: None
   Level: Warning
   Keywords: Classic
   User: N/A
   Computer: Test
   Description:
   A listener channel for protocol 'http' in worker process '3768' serving application pool 'PleskControlPanel' reported a listener channel failure. The data field contains the error number.
  

Cause

This is caused by a third-party ISAPI filter configured for the PleskControlPanel website, which cannot run at the same time as the Plesk rewrite filter.

Resolution

1. Connect to the server via RDP

2. Go to IIS > Sites > PleskControlPanel > ISAPI Filters > Remove third-party ISAPI filters, keep only the Plesk rewrite filter as shown in the following screenshot: