Why doesn't water pump to water container?

I have a Siemens Siwartherm 7400 Series IQ condenser dryer. We have taken it apart and checked the water pump as no water goes to the water container. The pump when put into a container of water, pumped the water to the tank but when it is all hooked up again, the water ends up not pumping to the container but ends up on the floor. Can't figure out why??