Overview
Call failures on Twilio — such as 404 errors or 'No Answer' statuses — can disrupt vital business communications. These issues often stem from factors like incorrect number formatting, unreachable devices, or carrier routing problems. This article provides a clear, step-by-step guide to help you diagnose and resolve common Twilio call failures, enabling smoother and more reliable customer interactions.
What You Need To Know
Understanding Twilio 404 Errors
When you receive a SIP 404 Not Found response during an outbound call via a carrier, it generally means that the carrier’s system does not recognize the destination number. This can happen for several reasons, including an invalid or unallocated number, a number that has not yet been ported, or incorrect number formatting. In some cases, the carrier may simply lack a routing table for the destination number, preventing the call from being properly routed through their network.
What Causes 'No Answer' Call Status?
A call is marked with a "No Answer" status in Twilio based on the behavior of the callee and the SIP response received from the carrier partner. This typically occurs in scenarios where the phone rings but is not answered, the device is turned off or unreachable, the call times out, or the call is neither actively rejected nor marked as busy.
Best Practices for Diagnosing Twilio Call Issues
- Ensure the destination number is formatted correctly in E.164 format (e.g., +3933XXXXXXXX for Italy).
- Place a test call from a regular phone (outside of Twilio) to verify if the number is reachable and rule out Twilio-specific issues.
- Use different caller IDs for test calls to determine if the issue is related to the originating number.
- Review Twilio call logs, including SIP response codes and call statuses, to pinpoint where the failure is occurring.
- Gather multiple recent call SIDs (within the last 48 hours) and detailed examples of the failure before reaching out to Twilio Support for assistance.
When to Reach Out for Help
If you've already confirmed that number formatting and connectivity are correct but continue to experience issues, collect recent call logs and test examples. Providing this information will enable Twilio Support to diagnose and resolve the problem more effectively, helping you restore uninterrupted communication faster.
Conclusion
Effectively troubleshooting Twilio call failures starts with checking number formatting, conducting tests outside the platform, and analyzing call logs. If issues persist, sharing detailed examples with Twilio Support ensures faster and more accurate resolution.