A user is getting the HTTP Error 503: Service Unavailable or an Event Viewer Error: Worker Process Encountered An Error - Cannot read configuration file. This error can have several causes.
On desktop versions of Windows, which are operating as a host/server for our software, the problem is frequently caused, and fixed, by the following:
On the browser, you will likely get a simple and uninformative HTTP 503 error message that does not provide any useful information about the actual cause of the problem.
However, if you look in the server's Event Viewer, you will find the following error message:
The worker process for application pool 'APP_POOL_NAME' encountered an error
'Cannot read configuration file ' trying to read configuration data from file '\\?\', line number '0'.
The data field contains the error code.
To fix this issue:
- Locate this folder on the server: C:\inetpub\temp\appPools.
- Within this folder, there should be subfolders that share the same names as the names of the App Pools seen in the IIS Manager. Delete these 'app pool' folders.
- Open a command prompt as Administrator and run the following command: IISRESET
- Open the IIS Manager and go into the Application Pools screen to verify that all application-specific app pools are started and that the DefaultAppPool is also started.
This should resolve the issue.