
Are you sure you're displaying deck 1 in the software? I know I've done it before where I had deck 3 showing and loaded a track to deck 1 but of course it doesn't show on the player because it's not visible. Try setting the view to 4 deck mode.
The other issue I've had before is if you have the deck-lock enabled (where you can't load to an active player), you have to hit the play/pause button first in order to make sure the playback is stopped -- even if there's nothing loaded and/or playing already.