I wanted to chime in with my own experience-- I also sat on the downstair for a while, unable to go down, re-reading the directions to try to figure out if I missed anything. In the end this was the issue--I always use right-shift for >, since it is on the same side, but the game only recognizes left-shift (and left-ctrl and left-alt). Using left-shift got me down to the next floor no problem.