Player unit switches and or dirty contact rivets on player unit .
Reels , check and clean 0-9 switches , the middle switch of the 0-9 might be dirty or not touching as this one need to be contacting , or reel wont power ,
Check score reset relays , manual operate these and It might begin to reset the score reels , to clean just run a bit of card strip through the contacts , gently close and wipe through , you can use alcohol or de natured spirits , let this evaporate before turning game back on

Found this animation from this thread on here https://pinside.com/pinball/forum/topic/gottlieb-2001-decagon-score-reels-sticking-on-9#post-1461630
https://images.pinside.com/9/03/8f/9038f0d7aa311136c423d88e5e579e4017dc8151.gif,

The 3 switches at the top are the 0-9 switches , your 10,000 unit wont have the 3rd (9) switch .The inner switch is the zero switch
The schematics posted by HowardR Top row , all in red shows when all score reels are on 0 , These all must be closed or else game wont complete the reset cycle.

gtbreel9 (resized).jpg

Just a note , its the middle switch , if that's not closed or not contacting the reel will not power , so check the middle switch first

Good work , now you know for the future , and really you just compare how the correct ones are working , they are a bit tricky to get adjusted properly sometimes , mainly its to much pressure on the switches and they wont move well when they get to position 9. cleaning the inner board and re-lubing the circuit board helps with this , Glad you sorted it and learned something