I'd check the Q relay. A misadjusted switch there would make the game think that it's in Game Over mode and never turn any of the playfield features or flippers on.

Is a ball getting kicked out of the outhole at all or is that dead, too?

Sorry, working without a schematic I didn't realize the Q relay wasn't going to be a Game Over relay in this game. My apologies. I wasn't trying to say the game would actually be in Game Over, but one of the switches that makes the game switch between being in Game Over to live might be misadjusted. On the Gottlieb schematic I had handy, all the flippers and playfield switches were connected to the main power line through a switch on the Q relay. Maybe that only holds true on certain models of Gottlieb multiplayer?

Anyway, I'd be looking for a switch that should be providing a path from the transformer to the flippers. The 6th position switch, as TimMe mentioned, might fit the bill. I'd be looking down the right side of the schematic for a switch that should be closed, but in your game actually isn't, even if it looks like it is.