Troubleshooting by symptom

Symptom	Check and safe next step
Setup unavailable on a managed computer	Use the instructor-managed VM route in setup; do not bypass restrictions.
Python or sudo missing	Run the preflight in Ubuntu, not PowerShell. Ask the VM administrator to provide the prerequisites.
Installation cannot download packages	Check approved network access; do not disable TLS verification or replace locked packages with unverified downloads.
Connection refused or wrong port	Follow port diagnostics. Do not stop an unfamiliar service.
Lab 1 authenticates unsuccessfully	Check .env locally and rerun bootstrap only on your dedicated course server after a password change.
Lab 2 register row missing	Verify the configured schema and your insert file; rerun the inspection query. Do not paste secret configuration in a report.
Lab 3 test failure	Inspect the first failure in .local/dbt-last.log; trace the violating row and your SQL change. Preserve tests.
Lab 4 docs unavailable	Complete Lab 4, run course.py docs, and open localhost:8080 on the same host. Stop another owned docs process if needed.
Lab 5 analyst query returns 42501	The masked-data query is intentionally denied; compare the role/action matrix. A denied permitted sales query needs investigation.
Lab 6 report interpreted as server log	Distinguish live client observations from the synthetic alert fixture; server evidence is Optional Lab 12.
Lab 7 fairness conclusion unclear	Recalculate denominators and compare error costs; equal rates alone do not establish fairness.
Optional server experiment fails	Follow isolated setup and recovery; do not reuse production databases.

Enrolled students send the lab number, command, expected result and a short redacted error to their instructor's private support route. Independent learners use the self-study help route. Never send .env, credentials, full logs or uncropped screenshots. Setup recovery explains private evidence and fresh DB/user configuration.

Author: Isaac K. Nti.