I was preparing my tractor mowing season. I removed the snow blade, sharpened the blades, lubs everything, and went to mount mower under tractor. The mower lift will not lower. The 3pt hitch goes up and down but mower arms barely move. Any ideas before I take it to the dealer? The cam arm rotates back and forth as I raise/lower the lever. I opened and closed the diverter valve a few times. Nothing.