Re: 12 Volt Power
OK...so you are plugged into power at your sisters house...right?
Are you sure you didn't pop the house breaker? Most house outlets are 15/20amps and a trailer can overload those.
Next...when plugged into the house, can you hear the converter running (small fan noise)
Next...with trailer unplugged from house...do the lights work? If so..do they get brighter when someone plugs in the trailer to the house power?
Do you have a volt meter? Can you test the battery/batteries with shore power disconnected?
Finally...double..triple check the reset button on your 12v bus bar. (shown below)