I ran into this issue the other day when I had to do a factory reset on my Cisco 7961 and after that it was stuck at the upgrading screen while displaying the MAC address on the bottom left.
Looking through various lists, it appears that others have ran into this issue before. Here are a few things you need to check for this to work
- DHCP ip helper-address
- Phone Load
- DHCP Scope
Most common issue is that folks forget to have the correct helper-address. In my case I was pointing the phone to the SUB whereas the DHCP server was the PUB. I try NOT to get firmware from my CME router and in all cases get it from the CUCM since that’s the easiest way to achieve this task.
I hope this was helpful!