did 50 amp GFI go bad??

A GFCI will not reset if the breaker feeding it has tripped. and if the ground fault still exists it will reset but immed trip.. How to tell the differnece.

Well, step one is to check the breaker.. if it's tripped you found the answer.. But once you have it working plug in an intentional ground fault (Say 10K resistor between hot and ground , either hot, should do it) and try to reset it, note the sound.

Now turn off the breaker and try to reset it,, Note the sound

now remove the test plug and restore the breaker and reset it.

However you have to do this when it is working properly.

The output wires behind the GFI have to be disconnected in order to test the device.

In addition, with the powering circuit LOCKED OUT, the rear and front of the GFI have to be carefully cleaned so as to remove any conductive residue. It doesn't take much leakage to make a ground fault interrupter circuit angry.

Where is this 50A GFI.......on the power pedestal OR inside your RV?

Why in the world do you have a 50 GFCI for your RV hookup.
The only place that would be required is a spa or hot tube.
More than likely you have a problem in the rig but GFCI do go bad but not often. I'd check with a good VOM (volt ohm meter) for a continuity between the ground and neutral in the rig. Of course with the power off !!!!!!
You should get no reading at all.
If you do something is amiss in the rig.
Other way is to turn off every circuit breaker in rig, turn on one by one and figure out which circuit is causing the problem and go from three.

Did you cycle it to the off position before trying to flip it to the on position. It will click when you push it to the off position, and will click again when going to the on position.

Yes, a GFI can go bad.

What happens if you try to reset it while there is no power to the coach? If you can reset it without power and when you turn the power back on and it trips, you have a problem.