Legacy F7 will not accept Commands from TMCC

You could remove the shell of the powered unit and see if the TMCC receiver has become dislodged from the RCMC.

TMCC receiver is the top board in the red outline.

Update (3 months later) - the Lionel authorized service center got the engine  couple of weeks after my (and GRJ) post.  Has had it for, now over three months and started by replacing the RCMC after a visual check of everything else.

It is still unresponsive to commands of any kind- TMCC, conventional, any.  It will not even come up in conventional mode.  When you power up the loco it takes off  at full tilt.  He cannot see any signs of an electronic failure anywhere else in the unit.

The authorized SC guy (who has spent years servicing Lionel with his now-deceased father- the original shop owner) contacted the Lionel service techs by phone.  They are puzzled as well.

Any ideas??

No ideas, but this is very similar to a current problem I’m having with a TMCC crane car. I did open the unit up (pretty tricky actually), and all the boards are seated okay. I’m sending it to a Lionel service center next week.  Good luck.