Locks are lit by completing the zones lit on the buikding. Ball one locks are lit at the shelter hole and side ramp. Once ball one is locked, no matter the shot, it ends up sitting in the subway in the lower right up kicker. Ball two is only locked on the side ramp and it stays there. A third ball should now feed to the shooter lane. Once the third ball hits a scoring switch multi ball will begin. There is also 'quick multiball' which is 2 ball which is lit in the eject/5 hole.
I would take a close look at all the ball sitting switches in test mode: all 3 trough, shooter lane, 2 subway switches on the lower end, eject hole, and top right up kicker.