You have a winterizing inlet on the outside of your camper for the uptake of antifreeze. This is connected to the intake on your pump. The water tank is also connected to the inlet on your pump. Right now the valve is turned to the winterized position and it is sucking air from the outside inlet.
2016 Rockwood Windjammer 3029W Diamond
2015 Chevy 3500HD LTZ 6.0 Crew Cab 4x4 Long Bed 4.10:1 SRW