"Check tel line" in handset display

You reset the modem as in removed power for about 10 seconds? Does the Internet work? If the Internet works and the phone doesn't and you've reset the modem you'll have to report it. 

I keep trying to report it, but I've had the same runaround with AT&T Support that others on this forum have had. Internet and TV still work. I tried reporting the phone to Support and was on the phone with AT&T for over 45 minutes. Twice I was misdirected to DirectTV techs. The chat just told me to unplug the modem for 10 seconds, then kept repeating it couldn't understand me. The last time I called I got cut off when they tried to transfer me. Absolutely zero support.

As fellow customers there's not much we can do about poor customer service. File an FCC complaint.

The problem is resolved. An AT&T phone support tech had to "push" my line from their end.

When I called the main support number, I kept getting DirectTV agents. Finally one of them gave me the number to call AT&T phone support, who was able to fix it.