Hoping you didn't tow the camper with no battery in it as that is against the Law. The trailer battery powers the brakes if there is a "break-away."
Your 7-pin pos goes on the pos battery post and the neg goes to the kingpin frame for the "ground" With no battery you might not have a positive "path" to the various trailer 12v items unless you use vice-grip pliers to connect the several red wires that normally go onto the battery pos post and get their path by being connected there.