Can you clarify which Cisco IP Phone model (88XX? 79XX)and on what platform it is registered (CUCM or CME)?
Good day George
We are using CISCO Unified CM Console (System version: 220.127.116.1101-3 Unrestricted)
Have the following CISCP Phone Models:
CISCO IP PHONES CP -6941
CISCO IP PHONES CP-6911
CISCO IP PHONES CP-7821
There's a Voice Server
You will need to connect via SSH to your CUCM Pub and issue the command "utils ntp status" to identify if everything is fine.
You may find all the info you need on the following post:
Hope This Helps