The answers to this question helped me and I thought a picture of the switch near the ball would help. I am pointing to the black switch with a pen in the photo. 3 screws and you can get too it. In the photo you can see the cover removed after the screws are taken out. Also mine looks slightly different as the wheels that hold it upright when stored broke so I just took them off.
As oldturkey03 said I would suspect the fuse first. Mine too was not powering up and when it did it would not recognizing the tray being in place. I took it apart looked for any easy electronic problems: fuse, burnt areas indicating over heating or failed electrical components / short, loose electrical connections etc. Never found what the exact problem was but something may have been loose because after doing the above and putting it back together it worked:)