[wingnut60]

Are the jacks a commercial unit for fifth wheels or some sort of one-off install?
Not a hydraulics expert, but you seem to be working in the right direction.
If the pump is working, but the jacks not--fluid is not being moved or is being bypassed somewhere. And, you hear the pump running, but maybe not pumping?
Have heard of valves sticking open, air in system, solenoids not working--could be any of those.
After market brands I have heard of are Big Foot and Rieco-Titan--either of these what you have?
Hope you get it figured out.