It’s been a while since I’ve used 9.12 but do you have the workflow state microflows set up correctly like below?
All of the workflow functionality was still in it’s infancy in early versions of 9. I’d recommend updating to something more recent like 9.21 and getting the updated workflow commons module. Any issues I originally had in early versions were fixed by making sure everything was updated and set up correctly as per the docs https://docs.mendix.com/appstore/modules/workflow-commons/