If the hydraulic unit is dry, you will need to have the system inspected to see what is the culprit. Possibly a latch or lock,
or one of the lifting rams or lines. The system is fairly complicated but, you may end up only needing a $100 line or ram.
The dealer should be able to diagnose it fairly quickly.
It takes less than 3 Hrs to expose the whole system.
good luck
DR.D