Most Lance campers use their own cord to connect to the truck. It has #8 wire for the 12 volt + and - conductors. With this size wire and the short distances involved with a truck camper it should charge just fine. It's not like a trailer camper connected to the stock 7 pin connector which has small wire running to it already.
The charge line on a Chevy does not come from the factory connected up. The wire is secured under the under-hood fuse box. It needs to be connected to one of the studs in the fuse box. There is normally not a fuse in there for that stud or sometimes a "dummy" fuse. I have no idea why GM decided shipping the trucks this way was a good idea.
With the truck running you should have 13.6 or more volts between the 12 volt + and - pins on the camper connecting cable. If you do and your battery doesn't charge then the problem is in your camper somewhere. If yo don't have voltage there the problem is in your truck somewhere.
