Unable to access Plesk: /usr/local/psa/admin/logs/panel.log cannot be opened with mode "a"

Symptoms

In an attempt to access Plesk, the process fails with the error below: 

PLESK_ERROR: ERROR: Zend_Log_Exception
"/usr/local/psa/admin/logs/panel.log" cannot be opened with mode "a"

Cause

Wrong ownerships/permissions for the /var/log/plesk/ directory or /var/log/plesk/panel.log file.

Resolution

1. Log into the the server via SSH.

2. Execute the command below to set proper ownerships/permissions for /var/log/plesk/ directory and files within it:
   

   # plesk repair fs -y