Recently one of our clients has a working CCM 4.3 and is using 7911 IP Phones both at HO and remote sites. All is working and fine, until we change the server with a new CUCM 7.0, all IP Phones at HO registered as expected and working, but IP Phones at remote sites was able to upgrade firmware but can no longer register, the IP Phones located at the remote sites just stuck with the Cisco logo. So we decide to get one ip phone and power it up at HO, it was able to register as expected. We then put it back to the remote site and the problem still persists.
To isolate, we then test the old CCM 4.3 back to the network and the same IP Phone located at the remote site register normally. Can you guys give inputs on this issue? I've check the TFTP logs and it looks fine.