You'll find either the contact on the hundreds reel need cleaning or adjusting. Just look at the 10's reel and see what happens when it reaches 9 - the lever usually shifts over to open/close contacts, then goes back on 0. The 100's reel should do the same thing.

The very bottom switch on the 100s reel switch stack has to close at the 9 position. Also, there's a switch on the 100s relay that must close.

That's the handicap for playing with the glass off. As KC said there is a arm that comes from behind your reels that moves a set of switches. There are three states of these switches. One state is when the reel is on 1-8. Another state when the reel is on 9 (This one might need attention as it advances the next reel). A third state of the switches is when reel is on 0 (this is important for startup)

Hi PJI5108
I like the ipdb-manual: http://mirror2.ipdb.org/files/415/Williams_1968_Cabaret_Instruction_Manual_no_schematics.pdf - on page-15 (ori-13) 3 switches are shown --- three times shown. Look at the bottom Switch - closed when the Unit is in Position-Nine.
Do NOT forget: This switch does close to let electricity flow - Switch MAY be faulty - OTHER possibility: The connecting wires - IF (if) a wire has broken-off from a Solder-Lug at a place --- This is the same as when the Switch would be faulty-open --- wire has broken-off means "NO connection" means "Your fault". Greetings Rolf