Plesk is not accessible after upgrade from Plesk Onyx to Plesk Obsidian: Unable to create file: C:/Program Files (x86)/Plesk/var/locks/authorizer.lock: Permission denied

Symptoms

• Plesk is not accessible:

  PLESK_INFO: HTTP Error 500.0 - Internal Server Error
  C:\Program Files (x86)\Plesk\admin\engine\php-cgi.exe - The FastCGI process exited unexpectedly

• Accessing Plesk directly on the server via RDP the following detailed information is shown:

  CONFIG_TEXT: Server Error
  500 Plesk\Lock\Exception
  Lock Manager error: 'Unable to create file: C:/Program Files (x86)/Plesk/var/locks/authorizer.lock: Permission denied'.

Cause

Missing user psaadm_users for the folder and all the subfolder/files of C:/Program Files (x86)/Plesk/var/locks/

Resolution

1. Connect to the server via RDP

2. Open properties of C:/Program Files (x86)/Plesk/var/locks/ folder mentioned in the error and switch to the Security tab.

3. Add the username psaadm_users with all the permission as allow:
   
   

4. Click Ok to save.