After plugging in a 2616 phone the display shows Model? (0) no matter what I do I can't get rid of it. I've tried other phones in the same line but it still won't work. The phone has a dial tone but can't make any calls. How do I get rid of the message and get the display back to showing date and time. Is it something to do with the way the phone has been programmed or does it have something to do with the way the phone line has been connected (hardware)?