Struggled to get the Cisco phone to work with FreePBX, nothing I did seemed to make it work.
Then I found a little nugget on information, Cisco 7960 (and I suspect other Cisco phones) have a limit on their password of 31 characters. [and they seem to simply truncate the string they are given in their Config file].
Whereas FreePBX when allocating a new line, allocates a 32 character random password (secret) - and if you are using a configuration manager (free or commercial) this 32 character password gets pushed automatically to the Cisco config file.
Simply deleting the last character of the password (secret) from Edit/Extension in FreePBX and it suddenly all springs into life!
Hope this helps someone.