Twilio is unable to process the Content-Type of the provided URL. Please see the Twilio Markup XML Documentation for more information on valid Content-Types.
You must return a Content-Type for all requests. Requests without a Content-Type will appear in the Debugger as a 502 Bad Gateway error.
- Having a phone number, outgoing call request or action attribute refer to a non-XML or audio resource.
- Having a Play verb attempt to play non-audio content, such as XML or text.
- Verify that that your web server is returning a Content-Type and it is the expected value
- Make sure the URL noted refers to a valid resource