Pads don't work and I can't even connect to the PC

I bought a used MPC-500, and the pads don't work, I press the mode button and when I press a pad, they don't work. The other buttons work, it has a 128 memory card, but it doesn't have extended memory, just the internal memory. Can someone help me?

It might be worth taking apart and seeing if the ribbon cable came loose or just needs to be reseated.

Try a reset , and if all the pad didn’t work again watch inside if the pad are plug corectly
Some time when you closed the mpc5000 after open it the cable who is plugged to the pad , disconected when the pad is moove before to screw it for closed
But if a reset ar not ok and if the pad are plug corectly and is not ok
You need to watch with multimeter if your bloc of pad are dead or not