Microbit: Sprite does not move

I'm making a game where player 1 has to dodge the boulders that player 2 throws at them. Player 2 automatically throws a boulder if there is not a boulder already on the screen. The problem is that the boulder does not move.

I've tried re-arranging the move and 500ms blocks around, and I've tried moving player 2 around, but it just creates another boulder.