When the game starts the flipper relay on the driver board should make an audible click. If you cannot hear it probably enabling issue related to connector MPU J4 Pin 7 to driver board J4 Pin 8. Examine back of board for cracked solder joints. The MPU J4 gets ate up by leaking batteries and cracked solder common there too.

If you can hear the flipper relay click but still no flippers check driver j2 pin 2 & 1 and driver j1 pin 8 & 9.

The displays themselves are single sided boards and the weight of the wiring harness and the when the door swings open it flexes on the connectors and eventually the solder joints crack. It is super common on these games that every single display will have bad solder joints from 40 years of flexing. I would start with making sure each display has good solder joints. If still have problems with displays then check out connectors at MPU J1.

Anyways.... connectors connectors connectors. usual problem. Its a pain to repin all the problem connectors in a game, but needs done in a lot of project games.