This inbound message appears to be machine generated. Responding to this message programmatically could lead to endless messaging loops. For that reason, Twilio has failed the message with this error code and did not POST to the number's configured TwiML URLs.
You are receiving a message that appears to be machine generated.
If you want to respond to these messages programmatically, you can listen for failed status callbacks with this error code and respond using the Twilio REST API.