Just to be sure and cover the basics:
I do not think you messed with your known track wiring or connections. That said, 2 possible things to check:
First since track1 did not work, and track 2 worked, swap the output channels of the TIU compared to track wiring (track1 to TIU fixed 2 output and track2 to TIU fixed 1) The idea being to ensure the track or say a car or other engine was not killing the DCS signal.
And while doing that, also check track polarity and the type of engine (PS2 VS PS3) engine you are testing. I say this, because PS2 engines care about polarity of the track compared to the TIU output (red to center rail, black to outside rail) where PS3 does not care and works either polarity. Again, there are scenarios where simple as wiring is crossed, a PS2 engine won't detect DCS signal and start in conventional, where a PS3 engine doesn't care about crossed wiring.
Signal failure of a channel can and does happen, just again trying to make sure it wasn't something simple and actual lack of DCS signal.
