When I press my thumb into the ball of cookie dough it cracks around the edges and won't stay together, what am I doing wrong?
That's a pretty common thing to get a bit of a crack when you press in. The more gentle you are as you press, the less it happens. But you can also "repair" the cracks by pushing gently together. If the dough seems too warm after that; chill for 15 min before baking.