i am afraid this is another one of those known bugs.

it's SUPPOSED to simply lift you up off the ground when you cast it. when it works correctly, you are supposed to just hover for a while. jumping, climbing, or walking will cancel the effect. i personally didn't use it except the one time i cast it to see what happened. i was never able to find a good use for it myself.

you could try casting it in a different area to see if you can get it to work. you pretty much need to be outside in order to make it work. a ceiling inside a building will thwart the effort.