Print Page - Plesk and sites show: HTTP error 503 - Application Request Routing\requestRouter

Title: Plesk and sites show: HTTP error 503 - Application Request Routing\requestRouter
Post by: Suhitha on Dec 17, 2025, 07:22 AM

Question: Plesk and sites show: HTTP error 503 - Application Request Routing\requestRouter.dll failed to load

Symptoms

Websites are not accessible with HTTP error 503
PleskControlPanel and most IIS application pools could not be started at IIS > Application Pools.
Event Viewer > Application log contains the following error under Event ID 2280

Code Select

The Module DLL C:\Program Files (x86)\IIS\Application Request Routing\requestRouter.dll failed to load. The data is the error.

Cause

Microsoft Application Request Routing package corrupted or missing.

Resolution

Download and install Application Request Routing package from Microsoft website:

Cobra Forum

Plesk Panel => Webserver => Topic started by: Suhitha on Dec 17, 2025, 07:22 AM