Everything else working? If yes, go into test mode, check switches (including optos, the optos that detect the ball striking Kenny have been known to be a problem). If the switches are OK, check the solenoid(s) that make him rock. Do they work in test mode? Visually inspect the solenoid(s), do they look burned? Cores and mechanism move by hand freely? Wires off solenoid lugs? Use manual to find the plugs where the solenoids are connected to driver board; plugs not burned? Gently flex the wires/connector while activating Kenny, if you get a reaction you may have a bad solder joint on pins.
Let us know how this diagnostic effort goes. They we can guide you from there.
Don C.