Define the symptom precisely
Record the exact objective, what you expected to happen, and the last event that definitely completed. A precise symptom is much easier to investigate.
Repeat the immediate prerequisite
If the route should follow a conversation, item, visit, or event, confirm that prerequisite first instead of trying unrelated activities.
Check the state around the trigger
Review time, location, inventory and earlier events. Keep the list short and relevant to the stalled objective.
Preserve the known-good state
If the current save works, keep an untouched copy. Experiment with a duplicate whenever possible.
Recognize a technical failure
Crashes, unreadable saves, missing files or application errors are different from an objective that simply has not triggered. Use technical troubleshooting for those cases.