Tail Number Tracking

Why can I no longer track flights by tail number? When I put in a tail number I can see the registration but no flight information.

What tail number?

As an example I tried to track N262PS which is a USAir Express plane.

There is no flight plan filed under N262PS, just the flight numbers it operates. FA does tie the flight/tail numbers for some airlines but PSA is not one of them (I think - where’s that ***** list ?).