GFI house breaker

After de-winterizing, and reconnecting the battery, when plugged into the house power, the POD trips the GFI breaker. It did not do this last year. NOTHING is even on in the R-pod. We took it camping and on power at the state park, all was well.
Could I have connected the battery incorrectly, ie. ground wire, or do I have an adapter problem....or something more serious ?

As Furpod said the GFCI have a limited lifespan, I have run into some weird cases. In my master bath I had one that only had and electric toothbrush plugged in, and if I plugged in a 3w nightlight in it the GFCI tripped (whaaa???). If you are handy with house electrical, I would replace that before troubleshooting the Rpod (takes 15 minutes and costs ~$10). Then you can also upgrade to a 20amp GFCI, you might have a 15amp at your house - since that is the cheaper "contractor grade" used in most construction.

Yes. Any hardware store should have them. Just make sure to find at least a 20amp rated one, since that is what the RV shore power adapter is rated for.

Only if the different outlet is a GFCI too. Otherwise you will not have an "apples to apples comparison".

If you replace the GFCI make sure it's a Spec or Contractor grade and Weather Resistant. My personal preference is to try find one that does not have the Tamper Resistant option. Most outlets come with the Tamper Resistant due to changes in the NEC.