You'll first want to check the switches in the ball count step up solenoid circuit. Check the following switches:

Trough switch - black/blue wire and orange/white wire
Game relay switch - orange/white wire

Make sure these switches are clean and adjusted properly. If these switches check out okay, then you'll need to look at the circuit that controls power to the game relay coil.

The game relay, depending on the machine, has a relation to the ball count unit and the coin relay...

If the game relay switch and the trough switch look okay, then verify that power can get to the ball count step up solenoid.

Power off the machine. You can adjust the two switches so they are always closed or you can tape the switches closed. Then power on the machine and start a game. The ball count step up solenoid should be constantly energized. Power off the machine and readjust the switches to their normal position. If this is the case, one of the switches in the circuit is not closing at the right time (most likely the game relay switch) and the circuit that controls power to that particular relay coil will need to be looked at...

If the ball count set up solenoid is not energized, then there's a broken wire in the circuit or there's a Jones plug problem on the main board. Or there is another switch in the circuit that isn't closing which would be shown on the schematic closer to the transformer...