We have recently upgraded to CUCM 8.5 and several of our 7911G failed to to register. I have tried factory reset but they just cycle throgh rebooting.
It has only affected a few, others have registered and are working fine. Any ideas
Couple of things to check.
1. Check for the number of licence DLU's available(Device License Units) in CUCM.
2. Also check the configurations for these phones are intact, if not you need to re-register them once again (auto register or manual registration).
3. Is DHCP enabled?
4. Alternate TFTP set?
5. Did you delete the security files and try once.
Hope it helps.
Alternate TFTP set
Phones worked fine prior to upgrade.
I have deleted them from CUCM to force new registration
Other phones work fine
Have tried 1234567890*# just cycles through Cisco logo and load screen
Have tried 3491672850*# blanks screen intermittent attempted reload
cannot delete unlock security as phone doesn't load
See if below link helps.