Keine Syncronisation der Domain Computer

Ich betreibe den UCS als Member in einen Windows Domain (Server 2012r2). Seit einiger Zeit werden die Computer nicht mehr syncronisiert, und Neue angelegte User werden ( zum Test ) nicht mehr gelöscht.
Im connector-ad.log hbe ich folgendes gefunden:

05.01.2022 13:09:58.832 LDAP (WARNING): Exception during search_ad_changes
05.01.2022 13:09:58.992 LDAP (WARNING): Traceback (most recent call last):
File “/usr/lib/python3/dist-packages/univention/connector/ad/init.py”, line 1891, in poll
changes = self.__search_ad_changes(show_deleted=show_deleted)
File “/usr/lib/python3/dist-packages/univention/connector/ad/init.py”, line 944, in __search_ad_changes
return sort_ad_changes(search_ad_changes_by_attribute(usn_filter), lastUSN)
File “/usr/lib/python3/dist-packages/univention/connector/ad/init.py”, line 922, in search_ad_changes_by_attribute
return self.__search_ad_partitions(filter=usnFilter, show_deleted=show_deleted)
File “/usr/lib/python3/dist-packages/univention/connector/ad/init.py”, line 849, in __search_ad_partitions
res += self.__search_ad(base, scope, filter, attrlist, show_deleted)
File “/usr/lib/python3/dist-packages/univention/connector/ad/init.py”, line 879, in __search_ad
rtype, rdata, rmsgid, serverctrls = self.lo_ad.lo.result3(msgid)
File “/usr/lib/python3/dist-packages/ldap/ldapobject.py”, line 749, in result3
resp_ctrl_classes=resp_ctrl_classes
File “/usr/lib/python3/dist-packages/ldap/ldapobject.py”, line 756, in result4
ldap_result = self._ldap_call(self._l.result4,msgid,all,timeout,add_ctrls,add_intermediates,add_extop)
File “/usr/lib/python3/dist-packages/ldap/ldapobject.py”, line 329, in _ldap_call
reraise(exc_type, exc_value, exc_traceback)
File “/usr/lib/python3/dist-packages/ldap/compat.py”, line 44, in reraise
raise exc_value
File “/usr/lib/python3/dist-packages/ldap/ldapobject.py”, line 313, in _ldap_call
result = func(*args,**kwargs)
ldap.UNAVAILABLE: {‘desc’: ‘Server is unavailable’}

Habt ihr eine Idee ?

Danke Axel