Maybe the problem is that they are mounted upside down? Is the one at the top working properly?
Leo - this is how they are meant to be installed, in my case at least. There is nothing, "at the top." Water is drawn via Sequence Dart via two in-takes to right (wall) side of tank down through bulkheads in bottom of overflow chamber. From Dart, located under cabinet, water is pushed into Ocean's Motions 4-way up to Revolutions (4) in tank bottom.