[wingnut60]

Here is something I would try: get a couple of bottle jacks and raise the trailer by the frame rails to get the jacks off the ground. Then see if they will go down/up without any weight on them. If they still don't move, then I don't think your pump is moving oil, or it is being bypassed back to the pump.
You need to figure out if any fluid is being moved by the pump--you know the motor is running, but is the pump moving any fluid? And if fluid is moving, where is it going?
This is getting past my ability to suggest anything else.
I looked at the Princess website, but did not find any obvious jacks, just cylinders. Do you have actual jacks or just cylinders attached to the frame?