From the manual, try this :
STANDARD PROCEDURE - RELIEVING HYDRAULIC PRESSURE
Note: The hydraulic pressure must be relieved before the top can manually be raised or lowered.
1. Turn the ignition to the “ON” position.
2. Push down on the convertible top switch and hold in that position.
3. Turn the ignition “OFF” and continue to push down on the switch 5 seconds.
4. After 5 seconds the hydraulic system pressure will be relieved.