Need some help

[Uprrman]

I just bought 2016 Salem lite travel trailer got it down to my lake lot hooked up my generator an surge protector got things up an running then I turned in the breaker for the micro way an it come up with a reverse polarity light then I shut everything off started it up an tried to plug in the outside frig an it started to blink the red light again what's going on its all new stuff an all new to me if I leave the outside frig is unplugged an the breaker for the microwave is off its all good