Fire the magnet via the test mode in the machines menu/test settings. If you hear the relay or magnet clicking in or out, place a ball near the magnet to see if the magnet works or not. If u hear the relay clicking, it probably means the magnet is fried only and you can replace the magnet easily. If you don't hear the relay clicking then it may be a loose wire or a problem on the board. Follow the wiring back from the magnet and check for disconnected wires or broken wires. Do you or your friend have a manual for the machine, would be worth checking the wiring diagram for the offending magnet and its circuit. Hope it helps.
