Need help with fuel gauge not working?

First and foremost I would check the voltage at the meter. I would assume that the wiring was damaged, clipped, shorted, open or any other possibility. Verify the voltage at the meter is correct and then work your way back to the tank. Check connections to the board. Are you using the original voltage limiter, now is a good time to get rid of it.
I just had the same problem with the temp gauge. First thing I did was replace the 5 vdc power supply to my meter. put it back together and works great.

If it fails all of a sudden. 99/100 times it is the source voltage. BTW, make sure the cluster is grounded properly