Unable to access Plesk: “The file /opt/psa/admin/htdocs/application.php is part of Plesk distribution. It cannot be run outside of Plesk environment.”

Symptoms

Unable to access Plesk. The following error is shown:

"The file /opt/psa/admin/htdocs/application.php is part of Plesk distribution. It cannot be run outside of Plesk environment."

Cause

Issue with Domain Traffic Monitor extension. It was already fixed and is scheduled to be shipped in the next product iteration. 

Resolution

Until the issue is fixed, proceed as follows:

1. Connect to the server via SSH;
2. Temporarily disable the extension:

   # plesk bin extension –disable traffic-monitor

3. Log into Plesk;
4. Go to Extensions > My Extensions > Domain Traffic Monitor > Updates > Click Check Now;
5. Select the new version and click Update to update it to 1.3.2-2:

   

6. Go back to Extensions > My Extensions > Domain Traffic Monitor > select Enable to re-enable it: