The drain pump is not working. I was cleaning the non return valve and the filters like they said in the manual but I don't know how to check the rest of the circuit to see if something is blocking the water. Can someone tell me what I need to do after I remove the no return valve in order to see the rest of the circuit? Maybe something is blocking the circuit and that's why the draining pump is not doing the job. Thank you for your time and support.