Unless you have impassable events in all 4 directions, then the most likely thing is that the tile the player is standing on is impassable. I would guess an impassable transparent tile was placed on layer 2 or 3 to erase (you should only ever use the one in the top left corner). I could, of course be wrong, but that is the most likely thing in my opinion. Run over the area directly around the hero with the erase tile (upper left) on both layer 2 and 3 and see if that fixes the problem. If it doesn't, upload the project.