I can't get the msg light to go off on my Panasonic KX-T7731 even though there are no msg's

What happens when you dial 700-0 on the intercom?

7731's work on 18 different Panasonic models, but they were first delivered with the later TA series phone systems. You could press the MESSAGE key and look at the display to see where the message came from, but I don't think you can erase it on a 7731. So, just record the fact, then 700-0 and poof. All gone.

Carl