For unknown reasons a CUCM may enter a maintenance state and fail to cleanly leave this condition.
When this occurs, the following message is returned when the Vyopta data collector attempts to poll for CDR records:
"CucmMaintenanceException for listFiles"
Whilst the CUCM is in this condition the data collector will not be able to retrieve call records.
The CUCM will need to be rebooted in order to clear this condition - as yet no means of causing the CUCM to cleanly leave the maintenance state has been determined.
In order to ascertain the cause of this issue, you may wish to raise a Cisco support case (TAC) before performing the reboot.