I have some phones where I added a secondary extension so users can see when the lobby phone is ringing. Problem is after adding 3 successfully when I add another user with a secondary extension they get a red X on the button. Could this be a licensing issue?
This is resolved turns out those phones with the red x had speed dial mapped to that button, I just configured the second extension on another button and now works. Funny thing is I called Cisco support and they tried to tell me you cannot have two extensions mapped to a phone.