The controller comes apart. I know it looks like it doesn't but it does. Flip it upside down and with your thumb press against one side of the controller that is stationary when you are using your machine. It should pop loose, then do the other side. It will snap back together. If it has a button on the outside but on the side of the controller push that button in while gently releasing the top of the controller by prying it loose with your fingers.