2017 New truck says 5th wheel it not connect? Update 8-4-18

If your DRV has separate turn signals and brake lamps, I would guess that is your problem. The new Super Duties somehow use the common brake lamp/turn signal circuit to sense the trailer. I ended up mounting 2 spare led lights in the battery compartment and wired them to the brake/turn circuit before it is split. Solved all problems including the truck's charge circuit not energizing.