Should have some more entries in the journalctl log with an error somewhere.
I’m wondering if you have the same issue here (Fail2ban wont start).
If you have an error like:
ERROR Found no accessible config files for 'filter.d/apache-api' under /etc/fail2ban
ERROR Unable to read the filter
ERROR Errors in jail 'apache-api'. Skipping...
then run this to resolve:
/var/www/html/admin/modules/sysadmin/hooks/fail2ban-apache-config