I am sure this is not news to a lot of you but if you are towing with an f-150 check to see that you have the relay and fuse installed for charging your camper battery. I came across this info in an...
Ford is not the only one to do that. When I bought my Chevy, I found that my Brake Controller worked but no brake lights and no battery charging. As you stated, it was missing a fuse but had the relay installed but it had to be turned around and re-inserted to work. Go Figure.