Hi JMPT
I agree with You --- everything in post-6 is true - the answer to Your question is: "The green".
In my JPG I drew it "blue" - somewhere there You have the fault --- want to make Yourself an 24Volt-Test-Light - car-lamps (cheap ones of course) are 12Volt --- we put two car-lamps in a line and have the Test-Light. SteveFury shows it here: https://pinside.com/pinball/forum/topic/reading-gottlieb-schematics#post-2634425 .
Make You such an Test-Light and hook-on permanent --- does it ever lights up ? It should light up in a short flash when the Score-Motor turns. Greetings Rolf