1962 Nova gas gage reads empty all the time even if tank is full. Any suggestions as to the problem? Gage was working before this problem.

Four guesses

The wire to the sending unit is shorted to ground.

There is no power to the gauge.

The gauge is defective.

The sending unit is defective. For example ,the float has a hole in it and stays at the bottom of the tank. Or the float arm corroded and broke.

There are lots of YouTubes about troubleshooting fuel gauges.

Disconnect the wire to the sender and the gauge should go to full. If it does, look inside the tank for the trouble. If not look in the car or the wiring.