Sip phones not registering on Asterisk

So currently setting up a new Asterisk system as our old hardware is showing it’s age. The current system is running Asterisk 1.8.7 and everything works fine, currently trying to get the new system up and running on Asterisk but the phone are refusing to register with Asterisk, I’m using the same config file as the old system uses with Asterisk 1.8.7.

I’m not seeing any messages on the Asterisk console either, Wireshark shows that the phones are trying to “Register” but Asterisk is replying with “Unauthorised”, but changing the new PBX system back to Asterisk 1.8.7 and the phones register straight away with no issues. I can get Blink (a softphone) to register without issue with Asterisk but not our normal office phones (Cisco IP Phone 7960 Series).

So what has changed between Asterisk 1.8.7 and Asterisk to cause this issue?
Have been going through the Asterisk change log but I have not found anything that jumps out at me.

Both systems are running the same version of Debian Squeeze and have been set up in the same manner.

Unauthorised is normal. The phone should respond by repeating the request with its credentials.

You are going to have to provide sip debug output.