This is typically an issue if you do not have enough suction from your pump. what is the reading on your pressure gauge? if it is below around 12 psi, there is insufficient flow for the cleaner to operate. look in the sight glass of the pump for air bubbles, which could indicate an air leak in the vacuum line, or too low a water line. try moving you filter handle to "waste" or "drain", see if it works on that setting. if it does, you likely need to change the sand in your filter. please let me know how these things check out, and we will go from there. good luck!