Thank you for sharing that you’re using Twilio and have already checked permissions. Let’s go through a few more settings together to help get this issue sorted out:
1.
Enable SIP REFER and PSTN Transfer: Please make sure that SIP REFER and "Enable PSTN Transfer" are turned on in your Twilio SIP trunk. These settings are essential for making call transfers via SIP REFER work smoothly.
2.
Disable TLS: Since SIP REFER doesn’t work with TLS for secure trunking, if you have TLS enabled, try disabling it to see if that helps with compatibility.
3.
Use Elastic SIP Trunking: If you’re currently using Twilio Programmable Voice with TwiML Bins, switching over to Twilio Elastic SIP Trunking might do the trick, as SIP REFER isn’t supported with TwiML Bins.
4.
Verify Trunk Configuration: It’s always good to double-check that your outbound trunk is set up correctly in LiveKit and that the SIP URI for the transfer destination is formatted properly and reachable.
If you try these steps and still face issues, please feel free to reach out. I’m here to help and we can explore other troubleshooting options together.
Sources:
Getting Help | livekit/livekit_composite | DeepWiki |
Agents telephony integration | LiveKit Docs |
Transferring calls | LiveKit Docs |
Secure trunking | LiveKit Docs |
Inbound calls with Twilio Voice | LiveKit Docs