Battery Not Charging Question

When we are hooked up to shore power the battery in the camper will charge. When hooked up to the truck it won't. I've looked in the truck manual and replaced, what I believe to be, the correct fuse and still nothing. All this seems to have started with a drained camper battery (left the antenna power button on). I hooked the truck umbilical power cord up to the camper and tried to run the slides out and they went out part way, then noticeably slowed down, like it was getting power from the truck for a bit then blew a fuse and went back to the camper battery before draining it completely. It sounded like there was some kind of audible alarm or something coming from inside the camper but it stopped before I could figure out where it was coming from. I can hook up jumper cables from the truck to the camper battery and it gets power, just not when I hook up the seven pin. Everything else on the seven pin works, all lights and brakes, just not the battery charge. Any thoughts or ideas are appreciated.