Well, it does work using the wire installed by ATC and grounding the panel to the roof.
I was only grounding the panel, using the grounding hole on the panel itself. When I used the negative wire it works fine. I can ground to the roof rack. Run a wire from the controller negative slot for the panel to the front camper window.
I haven't done a final install because I'm deciding how to install it. It seems running the wires from the panel direct to the controller seems much more appropriate, while doing all that grounding seems kind of hokey. I'm sure there was a reason for doing it that way.
Thanks for your assistance, it helped immensely.