Does the game over relay come on? The key is to isolate whether you just have a light issue or a relay/change of state issue. currieddog has given you the circuits in question. Another thing to consider it’s that there is a jones plug in between some of that logic.

So, score motor switch 1A, the Jones plug, the ball count unit, the ball index relay could be the issue if the game over relay doesn’t fire. If it does, then it’s a socket, or one set of contacts on the game over relay, the bill count unit, and probably a jones plug connection.

Good luck,
Dave