The manifold plate fell off.

I opened the dishwasher and the manifold plate was floating in my dishwasher, i put it back on but i unsure if the top arm is spinning. It looks like there may be a gasket that goes on the back side of the plate, there is a groove around the inside of the plate manifold side on the outer diameter of the circle gasket that is part of the plate, im not sure but it still has a seal that is built into the plate. Im not sure whats going on with it. I dont know if its spinning as ive started it let it run, opened it and the arm is in the same position, water is defintly flowing through it.