Hi
Don't have that game, but would look at the credit unit, even if the "0" switch is closed, the unit I believe shud still advance the credit wheel when coins are dropped. make sure it works manually, and the other switches work.
chk the ball count unit, make sure it goes all the way up/down manually.
if thats not it, maybe game over relay, or maybe tilt relay?
or...maybe start relay? kinda guessing here.

Issue #1: Check to see if there is voltage at the start/credit button switch. Also check the following switches in the start up circuit:

Reset relay - switch with yellow wire and red/black wire
Score motor switch IND-A - switch with red/black wire and white/gray wire
Replay button switch - switch with white/gray wire and white/orange wire
Replay step up unit credit switch - switch with white/orange wire and white/brown wire
Coin unit last position break switch - switch with white/brown wire and white/blue wire
Replay relay switch - switch with white/blue wire and red/brown wire
Score motor switch 5-A - switch with red/brown wire and yellow wire
Game over relay switch - switch with white/brown wire and white/blue wire
Ball count zero break switch - switch with white/brown wire and white/blue wire
Player unit zero break switch - switch with white/brown wire and white/blue wire

Make sure these switches are clean and adjusted properly...

Issue #2: Check the ball count unit to see if it operates correctly. Manually operate the ball count unit by pushing the ball count unit advance coil plunger. See if the ball count unit will advance smoothly to all the positions...