While accessing Tools & Settings > IP Address Banning (Fail2Ban) , the following error is shown:
Internal error: f2bmng failed: ERROR:f2bmng:Timeout of 10 seconds has been reached. Lock 'service.fail2ban' is already owned by another process with pid <unknown>
502 Bad Gateway
Incorrect/Incomplete installation of Fail2ban packages. When Plesk tries to get the service status for fail2ban, the process hangs and return a timeout error.
Reinstall fail2ban packages using