With slides In and jacks up check the res is it full? if not fill it up how old is the trailer and what make is the pump?Has any one played with the pump some have a control to adjust the flow some thing to look for also is a kink in the supply line to the jacks .Think of a floor jack a few pumps and a car is picked up. One more thing to check for dirt or plugged line ...I know that would be last on the list but a chunk of rubber line wall can plug as can part of a o-ring
