if "sudo systemctl status fail2ban" returns: 
    "ExecStart=/usr/bin/fail2ban-server -xf start (code=exited, status=255)"
and "sudo fail2ban-client -vvv -x start" returns: 
    "ERROR Failed during configuration: Have not found any log file for plesk-horde jail"
then identify the jail that is broken (in this case plesk-horde) and follow this:
    https://support.plesk.com/hc/en-us/articles/360027266234-Unable-to-activate-Fail2Ban-jails-or-start-Fail2Ban-No-file-s-found-for-glob-var-log-maillog