I'd examine the score unit. Is the stepper advancing when you manually push the plunger into the step-up coil on that unit? Does the score unit stepper reset crisply to the index position when you manually push the plunger into the reset coil? If not, you probably need to remove the wiper arms and clean the unit. When you start a game, what happens if you manually step up the score unit? The odds should advance. I'd first make sure the score unit is physically in good operational order. The circuitry that controls odds advances is an interaction between the spotting disc and mixers.

You're looking for something labeled "Score s.u. coil" (or similar wording) at the bottom of the schematic. s.u. means step-up.

That is correct. I forgot that your game has triple-deck scoring. If there is a circuit to one of those s.u. coils, the odds for that color should advance.