Moving your hands apart is just the first part of the motion.
As you move them apart the yo-yo will start to make the upwards pop motion, but you then need to move them closer together in order to give the yo-yo enough slack to rise above your hands. When the yo-yo rises above your hands you cross them and move them apart again to land the trick.
Watch our tutorial a few times if you haven’t already. The motion can be tricky at first, but you’ll get it with practice.