Connections, connections, connections. Your setup sounds OK, and I assume you've checked most of the obvious connections.
Be sure to check the control cable connections between the transceiver and the tuner. Use some De-Oxit on these, and other electrical
connections to be sure of good contact. BE VERY CAREFUL when opening the connectors at each end of the control cable. It's very easy to break something, bend a pin, etc.
Also, if it's not too hard to get to you might open the AT130 and check all the interior
connections, especially for the control cable. I found last year that a SG230 tuner which was 20+ years old and I assumed had failed suffered from loose interior
connections. Tightened them all up and Presto: the tuner came to life.
I assume you have either an M710 or a M700Pro....or maybe a M710RT. There's no M710Pro that I know of.