Unable to activate Fail2Ban: Unable to save the settings: f2bmng

Symptoms

When enabling Fail2Ban:

PLESK_ERROR: Unable to save the settings: f2bmng failed: Synchronizing state of fail2ban.service with SysV init with /lib/systemd/systemd-sysv-install...
Executing /lib/systemd/systemd-sysv-install enable fail2ban
Job for fail2ban.service failed because the control process exited with error code. See "systemctl status fail2ban.service" and "journalctl -xe" for details.
ERROR:f2bmng:Failed to start fail2ban service.

The server has Nginx + Apache

Following warning is while managing Fail2Ban in Tools&Settings > Fail2Ban > Settings:

Warning: Fail2Ban might not operate properly if there are many domains and Fail2Ban has to monitor too many log files.

Cause

Many domains in Plesk causing too many logs to read for Fail2Ban

Resolution

In Plesk > Tools&Settings > Fail2Ban > Jails, please edit plesk-apache-badbot and plesk-wordpress jails as follows:

Plesk > Tools&Settings > Fail2Ban > Jails > <jail-name> > Change settings, and replace:

PLESK_INFO: logpath = /var/www/vhosts/system/*/logs/*access*log

by

PLESK_INFO: logpath =  var/www/vhosts/system/*/logs/access*log

Then on Plesk > Tools&Settings > Fail2Ban > Settings:

Check Enable intrusion detection and click OK/Apply