Fuel gauge Intermittently worked,..now nothing. 66 Valiant

I'm really not sure why the pulse voltage would go away. Can a faulty limiter operate 1 gauge, within reason at least, but not operate 2. Heck anything is possible, even if not typical.
The pulses are supposed to be 2.X and 3.X to average about 6 volts. Much easier to measure with analog meter.
Just for fun... I would disconnect the temp sender and retest the fuel gauge for the slightest movement.
If the fault does turn out to be the limiter, or just a failing connection there, it's best to pull the panel to replace it.