Times 2 what Rgatijnet1 said. We just experienced this yesterday at the park we are in, and had to move over one spot. The 50 amp would not go through the switch to the coach. It will detect things like low voltage on one leg or a loose ground in the power pedestal. Also, I agree with what someone else said in not running the generator while plugged in or vice versa. In the time we have owned this coach, we have encountered this problem 3 other times. One was a loose ground in the pedestal and another was a leg low on voltage. The other time, the park chose not to investigate it till after we left. Another rig with a different transfer switch may power up fine where yours would not, that also has happened to us. Hope this may help, Happy Trails Bert