The listener seems not to be up and running. It appears to be out of sync. Nagios reports errors as follows:
UNIVENTION_REPLICATION CRITICAL 2018-12-04 09:49:20 0d 1h 10m 38s 5/5 CRITICAL: no change of listener transaction id for last 10 checks (nid=240976 lid=cat: /var/lib/univention-directory-listener/notifier_id: No such file or directory)
/var/log/univention/listener.log you might see entries like this:
04.12.18 08:48:47.597 LISTENER ( ERROR ) : import of filename=/usr/lib/univention-directory-listener/system/company_name-offboarding.py failed
You have configured an additional listener module which appears to fail for some reason so the listener does not start correctly.
Remove your listener module or perform troubleshooting why it fails.