The workflow executes and appears to reach the End without an error but is Paused and one or more activity/steps are still blinking blue.
Or an activity might blink red and you will see an error in the journal stating 'The computation step must have at least one inbound transition.'
One or more transitions before the error/pause point are blinking orange (a major clue.)
Not all of your activities are connected.
For any that are disconnected, drag and drop them onto the incoming transition head.
When diagramming the workflow, move activities around. Connected activities should stay connected; the transition arrows follow them.