Cobra 29 LX Max T Back disabled all audio, also can't transmit.

I have a lightly used Cobra 29 LX Max, that I bought from my brother which he bought new and only used it a few times. I installed it in my Jeep and it worked great for about a month. Now it’s acting really strange. When I had T Back switched off, all audio turns off, even the weather channel is quiet. I see the Receive indicator on the LCD lighting up, but can’t hear anything. I switch T Back back on, even at the lowest volume, and all my audio volume comes back on.

Also, when I key down the mic, the meter swings over but doesn’t move when I talk into it. No one can hear me, and also T Back doesn’t repeat anything I say. They can hear me key down over the air, just no voice comes through.

I’ve calibrated my antenna, also switched to another magnet that was also calibrated. They both do the same thing. I did make sure the test antenna was on the body of my Jeep for ground. I’ve opened the CB but down see anything obvious. No burns, no mud, no loose wires. I’m not afraid of soldering, just looking to some people with experience before I start anything crazy. Any help would be greatly appreciated.