I believe that with TMCC StationSounds diners the lights are on by default when there is power to the track IF (1) the light switch under the car is set to the ON position (if it’s OFF the TMCC command won’t override it) and (2) no lights in the car have burned out - they are incandescent and I think wired in series. With the switch set to ON you are meant to be able to toggle the lights on and off by an AUX1-8 keypress and I suppose if last operated with the lights off you might have to enter that command to turn them on, but that is not the default setting as far as I recall.
No sound or light indicates a power supply failure to me and I’d check the wires from the trucks. Beyond that the next thing that occurs to me is a radio board failure but it could be any one of several things.
