TNC Not Transmit


I have a TM-D710A in a fixed station. I hadn't exercised the APRS in a while and decided to transmit a few packets. I hit BCON and no TX. I'm not using a GPS and have it set to use a single location. Nothing has changed in my setup or memories. I decided to try Winlink. Winlink will connect to the radio and put it in packet mode. When I tell it to connect... Nothing. Eventually it times out. I figure... the TNC must have gotten SNAFU'd and did a FULL reset. I put my callsign and SSID in, did minimum to get it to beacon APRS... Nothing. Yes... the squelch is closed... no 'busy' on either band. So I set it to beacon every 3 min. I turn the tx beep on so I will hear it beacon and I hear the beep but no "on air" TX. It beeps every three minutes faithfully but no TX.  So... I try to manually get the TNC to transmit the only way I know how.. I get PuTTY going and connect. I'm able to send and receive commands to the TNC, I'm able to receive packets and read them with PuTTY. The TNC is working. When I send the C command and a callsign I know is on the air, nothing... no tx. It eventually times out. 

I'm about to pull my hair out. Audio in and out is fine. No problem using it as an FM radio through repeaters. Audio reports are fine. I pulled the nearly dead battery out of the head and ordered a new one. Left it over night and put the old one  in the next day. That did not fix it. I even reinstalled the firmware for the head unit. That required a full reset again. It just will not TX from the TNC. Even tried to send an APRS message and nothing. I have tried three different cables to connect the head to the radio.. nope.

Can the head unit's battery being very flat (only keeps clock a couple of minutes after turning it off) cause this behavior? I mentioned I have new ones on order but can't test yet as they won't be here for a few days. Does anyone else know what else to try? I am not the first owner and opening it up, the only thing that looks obvious is that it has been modded for MARS/CAP. I cannot see the board that has the jacks for the mic and the control head without pulling the main board which I'm hesitant to do since it looks pretty pristine. I have posted this on the Facebook group so please ignore me if you have read all this before... thanks
Dusty, NR4N