What happens if the NCCO download request fails?


  • Why is my NCCO being requested from my answerUrl multiple times?
  • Why does my call fail with "failed to retrieve the ncco"?
  • Will the Voice API retry the NCCO download request if my answerUrl fails?
  • Why do my calls fail after 1 second?
  • Why am I getting "General SSLEngine problem"?
  • Why is the event callback being sent to my fallback answerUrl?



If the Voice API encounters an issue when downloading your NCCO using GET or POST, depending on the method you have configured in your Application or the method that has been set in your API request, it may reattempt the request.

The Voice API will retry the GET or POST request once more if:

The Voice API will not retry the GET or POST request if:

  • Your server responds with an HTTP response stating an error other than 429, 503 or 504 (e.g. 404, 401, 500...)
  • Your NCCO has a syntax error (e.g. missing [ or invalid action)
  • The NCCO is encoded incorrectly (e.g. text/html, application/xml...)
  • The answerUrl or eventUrl is invalid
  • There is an issue with your SSL certificate (e.g. self-signed certificates without a certificate authority, intermediate certificate isn't being returned, etc.)

If your answerUrl or eventUrl fails to return a 200 OK or returns an invalid NCCO, and you have provided a fallback answerUrl, this will then be used to request the NCCO.

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