Waste water flush

I recently bought a 2016 Durango Gold G366FBT fifth wheel. So far I have no complaints. I have a few questions about the waste water tanks. I have two tanks, one (closest to the hitch) that drains the toilet in the main bathroom and one toward the rear of the trailer that drains the downstairs toilet. In the control panel box there are two black fittings. One is on the face of the control panel and is stamped "tank flush" underneath. The other fitting is actually in the side of the control panel box. When I connect my flush water source to the fitting on the side of the control panel box I hear the "flippers" inside the back tank (the downstairs toilet) and water flows out of the tank. I do not hear water running in the front tank (next to the hitch) and don't get water flowing out of the tank. When I connect the flush water source to the fitting on the control panel face I don't get water into either tank. (1) How do I flush the front tank? (2) Does it also have "flippers" to help clean the tank? Any help will be appreciated.