Update AZ400_M00_Validate_lab_environment.md

Instructions/Labs/AZ400_M00_Validate_lab_environment.md

@@ -27,5 +27,7 @@ lab:
 16. **Wait at least 3 hours before using the CI/CD capabilities** so that the new settings are reflected in the back end. Otherwise, you will still see the message *"This agent is not running because you have reached the maximum number of requests…"*.
 17. In Organization Settings, go to Security -> **Policies**
 18. **Turn on** "Third-party application access via OAuth"
+    > Note: The OAuth setting helps enable tools such as the DemoDevOpsGenerator to register extensions. Without this, several labs may fail due to a lack of the required extensions.
 19. **Turn on** "Allow public projects"
+    > Note: The public projects setting will allow some of the labs to use the free version of some extensions.
 20. OPTIONAL: you can validate this new setting has been successfully applied by creating and triggering a build pipeline. To do this either talk to the instructor or create a demo project into the newly created organization with billing enabled, using [Azure DevOps Demo Generator](https://azuredevopsdemogenerator.azurewebsites.net).