Make sure there is nothing preventing the wheels from going all the way against the housing that they spin on. If they do it should be on the ground. You may also need to make sure your lift lever doesn't have the lock mechanism set somewhere to prevent it from going to the bottom. :dunno:
Check the cam under the height knob, you can see it by looking past the left rear tire. The rock shaft arm should slide up through the open slot on the step cam. if it doesn't try turning your knob until it does, your knob may not be lined up. so your knob says its on install, but the cam gear is at the 2 inch position. Other possibilities, if you have an implement on your 3 pt arms like a tiller, your deck may not go all the way down. If you have a BH on, your power beyond line may be getting caught under the rear arms.