Start with the webhook URL and its registration state. n8n creates separate Test and Production URLs. A test endpoint requires an active listening session; a persistent integration needs the Production URL and a published workflow. Older releases may label the control as activation. 1
Check these before rebuilding the workflow
Compare the URL saved in the external service with the one displayed by the Webhook node. Copy the correct address instead of manually rewriting a test URL. Check the HTTP method too: opening a link in a browser does not reproduce a POST request. 2
For testing, select Listen for test event and send the request during its listening window. For an integration that must work after closing the editor, use the published workflow’s Production URL. 1
Identify which server returned the error
An n8n “not registered” response points you toward the endpoint, method and workflow state. A proxy’s HTML error page suggests the request may not have reached n8n at all.
Look for a matching execution. If none exists, rewriting a downstream AI prompt is unlikely to help. If an execution exists, follow its node-level results instead.
Use fictional test data. Replaying a real customer request can trigger duplicate actions once the endpoint starts working. A successful test should prove routing without creating a second order, email or CRM record.
Related reading
Web development and integrations
