This sounds as though it lost all saved channels and lost the ability to detect broadcasts.
Hook up a vcr or other device (example, rf modulator) that provides output on channel 3 or 4. It's a way you can check whether your tv still is still able to handle rf signals. If it works then execute the auto-program routine, to see if it saves the channel coming from the vcr.
If it fails then test it with a signal from a DVD or other player that produces video (composite, or RGB, etc.).
One time we lost our cable tv signal all of a sudden. After fiddling with every connector on every splitter throughout the house, I finally fixed it by sanding/scraping the center wire in the incoming cable connector (located in the garage). I'm pretty sure it was tarnish. A year or two later it happened again.