GFCI at shore power tripping

So here in Bellingham we just got an out of the blue cold snap and snow and I don't want to put water in my hot water tank to start my testing/pinpointing until it gets a few degrees warmer. That being said, when I went to drain the tank by removing the anode rod, I noticed that the trip button on the tank has been tripped. That tells me it is an issue within that hot water tank circuit. I also installed a 12 gauge extension cord and dogbone electrical adapter that will be better suited than what I had. Just wanted to keep folks in the loop. So until some warmer weather comes, we are in a holding pattern.