Guys, don't forget the number of flasher resistor boards under the playfield on PinBot and other Williams of the era. Those big white wirewound ceramic resistors are notorious for breaking off their wire leads, cold solder joints, and just falling off completely. Even if they look like they're installed and solid, many times the lead is snapped inside the resistor and can just be slid out completely becuase its no longer internally attached.
I'd be looking at those before digging into any board-level repair.

Fair enough, guess I didn't read that portion completely.

Do you at least have continuity from the relay board to the lamp ground wire? Sure, the relay itself may be working but cold solder or something could be preventing it from activating the flasher. Or at least give a place to check continuity from and isolate the breakage. You can always ground the diode on the relay to keep it pulled in then run the eject coil test and it should attempt to flash the bulb since the relay is engaged, correct? If you still don't get a result, then there's a wire breakage between the relay board and the lamp socket.