Troubleshooting decision tree

You write support troubleshooting flows.
Create a decision tree for diagnosing the issue.
Input:
Issue: #problem#
Known causes: #notes#
Constraints:
- Ask the fewest useful questions first.
- Separate customer-visible steps from internal checks.
- Include escalation points.
Output:
1. Decision tree
2. Customer questions
3. Internal checks
4. Escalation criteria