Issue
When making outbound calls using Twilio’s Programmable Voice and SIP trunking (for example, through Asterisk), you may encounter a 404 Not Found error. This article explains what this error means, why it occurs, and how to resolve it.
What is a 404 Not Found Error?
A 404 Not Found error in Twilio’s Programmable Voice indicates that the destination phone number dialed is not recognized or cannot be routed by any carrier. This is not an issue with your Twilio account or SIP trunk configuration, but rather with the validity or reachability of the number you are trying to call.
Product
Twilio Programmable Voice, Elastic SIP Trunking
Cause
- Invalid or Mistyped Number: The phone number may not exist or may be incorrectly formatted.
- Number Not Available: The number is not active or has been disconnected.
- Carrier Routing Issues: No carrier is able to route the call to the destination number.
- Country or Region Restrictions: Some numbers may be restricted or not supported for outbound calls.
Example Scenario
A customer using Twilio SIP trunking with Asterisk attempted to call several Australian numbers and received 404 errors. Twilio logs showed:
- Calls were sent from Twilio to the PSTN (Public Switched Telephone Network).
- Multiple carriers were tried to maximize connection chances.
- All attempts returned 404 Not Found, meaning the numbers could not be reached.
Resolution
- Verify the Number Format
- Ensure the number is in E.164 format (e.g., +61278086311 for Australia).
- Double-check for typos or missing digits.
- Check Number Validity
- Confirm the number is active and able to receive calls.
- Try calling the number from a regular phone to see if it connects.
- Review Twilio Call Logs
- Use the Twilio Console or API to review call logs and error codes.
- Look for repeated 404 errors across different numbers.
- Consider Carrier Restrictions
- Some numbers may be restricted or not supported for outbound calls.
- If possible, test with other numbers in the same region.
- Contact the Number Owner
- If the number belongs to a business or individual, confirm it is operational.
What to Do If the Issue Persists?
If you have verified the number and still receive 404 errors:
- Try calling other numbers to determine if the issue is isolated.
- Review your SIP trunk and outbound call configuration for errors.
If you need further assistance, gather the following information:
- The affected phone numbers (in E.164 format)
- Call SIDs from Twilio logs
- Date and time of the failed calls
- Any relevant error messages