First , I do not have one of these units. I may have an answer. Depending on HOW long ago it has been since you last used the unit, the seals may be dry, and running the pads up and down several times ( you may have tried this) may help.
The oil may be very low, or the pump its self may be too old to work properly. BUT a 2002 should not have that much of a problem.
Hydraulics always have a filter in the line some where. It may be plugged? or the small limit switch is out of place.
I would suggest if not already done , change the oil and the filter, in that you will also have to drain the cylinders to do it properly. Then re-fill and bleed the system to get the air out ,, THAT may be the problem also . It may just need the system to be "bled" or the air removed. Something similar to the car brakes if they don't work properly.
That is all I can think of
Good luck
Chuck