There was a failure attempting to retrieve the contents of this URL.
An 11200 error is an indicator of a connection failure between Twilio and your service. When Twilio requests a page from your server, we wait a maximum of 15 seconds for a response. A connection failure will occur if no response is returned in that time.
There are many reasons a connection timeout can occur; common causes are long running database queries or outside processes and calls to external systems taking a long time to return. It may be possible your application experienced one of these issues. If you are encountering this error only intermittently, it is possible that your web server was temporarily unavailable or experiencing a network outage.
If your debugger is reporting a 502 Bad Gateway error, this may mean that Twilio's internal server had trouble retrieving content from your website. Your request must contain a Content-Type that is valid. Twilio may also have had problems resolving your DNS name to an IP address, or issues with the network connection. Check that your web server is started, and is available over the public Internet.
Content-Type: audio/x-wav, instead of