Unable to start Fail2ban: found no accessible config files

Symptoms

•  "Switch On" Button is either missing or it does not activate jails at Tools & Settings > IP Address Banning.
• Fail2Ban is not active at Tools & Settings > Services Management.
• The following errors are shown when trying to enable Fail2ban:

  PLESK_ERROR: vps-53a4494f fail2ban-server[19023]: fail2ban.configreader [19023]: ERROR Found no accessible config files for 'filter.d/murmur' under /etc/fail2ban
  vps-53a4494f fail2ban-server[19023]: fail2ban.jailreader [19023]: ERROR Unable to read the filter 'murmur'
  vps-53a4494f fail2ban-server[19023]: fail2ban.jailsreader [19023]: ERROR Errors in jail 'murmur'. Skipping...
  vps-53a4494f fail2ban-server[19023]: fail2ban.jailreader [19023]: ERROR No file(s) found for glob /var/log/proftpd/proftpd.log
  vps-53a4494f fail2ban-server[19023]: fail2ban [19023]: ERROR Failed during configuration: Have not found any log file for proftpd jail
  vps-53a4494f fail2ban-server[19023]: fail2ban [19023]: ERROR Async configuration of server failed
  vps-53a4494f fail2ban-client[19027]: fail2ban [19027]: ERROR Failed to access socket path: /var/run/fail2ban/fail2ban.sock. Is fail2ban running?

• Fail2Ban looks for a non-existent log of a package that is currently not installed on the server, which in this example is mumble-server.

  # service mumble-server status
  Unit mumble-server.service could not be found.

Cause

Fail2Ban scans for log services installed on the server. It cannot start if there are activated jails for packages that are not installed.

Resolution

1. Log into Plesk

2. Go to the Tools & Settings > IP Address Banning.

3. Switch off the unnecessary jail/jails:
   

4. Start Fail2Ban at Tools & Settings > Services Management.