Phonebridge Twilio not working at all

I have configured my CRM account to use Twilio for Phonebridge, but I am unable to make any call or receive any calls. I have configured the integration correctly, verifying within Twilio that Zoho CRM has registered their URL REST endpoint with my Twilio number. I have set up the number within my CRM but whenever I attempt to call the number or make an outgoing call, I get the same response, "Your call cannot be complete", which is what is specified by Zoho as evidenced by this output when I bring up the URL that Zoho configured in my Twilio account.

<Response>

<Say>

Your call could not be completed. Please call back a little later.

</Say>

</Response>

 Is there anything I need to do or is this a problem on your end?