We encountered a case yesterday where we registered a retell call to bridge from Twilio, but Twilio encountered an error when trying to connect to the SIP endpoint. Our client is asking us for more detail about the cause of the error, but we cannot see anything in Retell. The call does not even appear in our call activity log in the workspace - org_PDjHnTQRj7NzJISI. The retell call ID was call_b011a101d240031af4a7e683113. The full error from Twilio:
When using the Dial to SIP URI method, if Twilio fails to connect to the SIP endpoint (sip:call_id@sip.retellai.com), the call never actually reaches Retell’s servers. That’s why the call does not appear in your Retell call activity log — Retell only records calls that successfully establish a SIP connection.
Twilio error 32011 indicates a SIP connectivity issue on Twilio’s side. We recommends checking logs in your telephony provider and opening a ticket with them for connection failures.
Since the call never connected to Retell, Retell has no additional error detail to provide. The root cause investigation needs to happen on the Twilio side using their logs and error details.