Unable to access Plesk for Windows: 503 Service Unavailable

Symptoms

• When accessing Plesk, the following error appears in a browser:

  CONFIG_TEXT: Service Unavailable.
  HTTP Error 503. The service is unavailable.

• The PleskControlPanel application pool at IIS Manager > hostname > Application Pools is stopped. After starting it manually, the application pool stops on the next attempt to open Plesk in a browser.

• The following error messages appear in the Event Viewer > Windows Logs > Application: 

  CONFIG_TEXT: The worker process for application pool 'PleskControlPanel' encountered an error
  'Cannot read configuration file due to insufficient permissions
  ' trying to read configuration data from file '?\C:\inetpub\temp\apppools\PleskControlPanel\PleskControlPanel.config', line number '0'.
  The data field contains the error code. 

• The following articles do not solve the issue Plesk for Windows Server shows 503 Service Unavailable: Cannot read configuration file or How to reconfigure the PleskControlPanel website in IIS

Cause

Lack of permissions for the psaadm user for C:\Inetpub\temp location.

Resolution

1. Connect to a Plesk server via RDP.

2. On Windows Explorer, right-click on C:\Inetpub\temp;

3. Go to Properties > Security (tab) > Advanced >select psaadm > click on Edit;

4. Make sure that its NTFS permissions are set as follows:
   
   

   Note: In case there is an explicit Deny enabled for the psaadm user or it is inherited, remove it and disable inheritance.

5. Start the PleskControlPanel application pool at IIS Manager > hostname > Application Pools;

6. Access Plesk