All extenstions cannot log in

Some phones do not register based upon where they are trying to log in from.

I can log in my CISCO phone and receive calls. I can change that phone to another extension and receive calls. When I move that phone to another physical office building location (different network) the phone appears to register but does not receive calls nor can calls be made.

Also I use Zoiper and it will only register when I am on my home network.