Hi
Have you inadvertantly clicked the Enabled Track Solo for Track 1 at the left end of the track? .....it will show a single "pawn" instead of group. This will disable and darken the overlay track as you describe. If so simply reclick it.
Have you disabled the output on Track 2? The "Eye" icon at the left will be red. If so reclick it.
There was a similar post with same/similar problem just recently.......but cant find it.
Edit
Might be here...
Nat