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.
<?xml version="1.0" encoding="UTF-8"?>
)<Response>
element is missing< > and &
.