Does the lever seem to go all the way? Take the cover off the box and look closely at how far the raise-lower valve is actually moving - try pushing directly on the valve stem to see if it will go far enough to release pressure. If it's being blocked it might have water or oil in the bottom cap restricting valve travel. The cap is usually removable (4 srews) Some have reported drilling a tiny hole in the cap to allow any oil or water to drain out. Hope this helps.