GFCI help

Hi all!

Technical help requested.

We have a 2012 2720 (last off line prior to closing/reopening) which has been in our possession since June 2011. We camped all last year no problems. It has been in garage storage Oct - April in NH.

We pulled it out 3 weeks ago - connected it to shore power, no issues. All elecrical systems go. I just got propane filled yesterday and all propane systems go - hot water heater, furnace, shore water pressure...all good.

Kids went to sleep in it (per usual) with electric heater on (habit, since propane hadn't been filled), clock plugged in. Somewhere between 9 pm - 8 am the GFCI tripped and the indoor outlets no longer work. The GFCI feels "spongy" and will not reset.

What have we checked?

Fuses - replaced (although not necessary, I now know)
Shore outlet - works
Connector plug - works
Extension cord - works

Removed GFCI outlet, and 2 black wires were not connected; we connected those, and when we reconnected shore power we briefly heard a fan noise near the main circuit box/no outlet power at all, no GFCI reset.

(BTW, no external outlets work either)

I just saw on the board that a blown water heater element can cause GFCI to trip - too dark to check that now, but I will.

ALSO - we did have mice in the camper much to our dismay. Investigation reveals no obvious damage, and due to food left over (we found the food source and no cushions destroyed) it appears they were in there a week or two max.

Why would the outlets stop overnight?

Mice were known
Water was tested yesterday 2pm and drained (low drains) 9pm; it has rained 2/3 weeks since we pulled it out and the camper has been set up.

Any and all suggestions are welcome.

I will check the water heater element tomorrow; I am prepared to replace that GFCI outlet if needed. If these 2 fail, then probably back to dealer for mice damage inspection...

Thanks in advance for any / all suggestions

bigd13