[Fulltiming]

Tom is correct. Expanding on a couple of the items he mentioned. If you have a manual transfer switch with a control switch close to the driver to switch between Shorepower and Generator, your transfer switch has, in addition to the two large relays, 2 small relays to prevent accidentally energizing both circuits at the same time. If one of these small relays gets debris in them (they are not sealed), it can cause the transfer switch to fail to switch over. That happened to me once. I turned off the generator, made sure shorepower was not connected, disconnected the inverter, then removed the small relays one at a time and found one with some hay in it. I cleaned it out, reinstalled it and all was well.

I have heard from others that they have had the breakers on the generator itself trip. Resetting the breakers may solve the problem or, if they trip again, indicate and issue with the head on your generator.