Twilio was unable to parse the provided XML Document.
Your TwiML document must be a valid XML Document, or Twilio will not be able to read your document. You can debug XML parsing errors by getting the response body in the debugger, and then using an online validation tool like the W3C Validation Service.
Twilio's HTTP client does not support chunked transfer encoding. If your server
responds to a request for TwiML with the HTTP header '
chunked' and your TwiML document is larger than the size of one chunk, it will
be truncated, which often results in a 12100 error. Dividing up large TwiML
documents into smaller sections and using multiple
verbs to route between them is the best way to get around this issue.
<?xml version="1.0" encoding="UTF-8"?>)
<Response>element is missing
< > and &.