There is a great animation of the score reels and switch positions in this thread. Make sure your reels are the same. In there zero position, all 3 switches need to be open.
https://pinside.com/pinball/forum/topic/williams-score-reel-operation-animation
Those score reels are usually easy to work on(at least compared to Gottllieb). Are you pulling the reels out of their metal frame?