Reverse Polarity?
 

I put my boat away for winter and attempted to use an adapter for the shorepower so I can plug it into a wall outlet. I plugged it in and a warning light lit up on my switch panel that says "reverse polarity". I know what reverse polarity is, but I do not know in this situation would cause that light to come on. I never had a problem this year with my shorepower, so I'm assuming it has something to do with that adapter.

Mine did that this year also. It turned out to be the adapter wasn't correctly put togrther. wasn't all the way tight. Check all your connections. Hope this helps