Issue: Outbound SIP trunk not initiating calls to Twilio - 403 Forbidden I'm experiencing an issue with outbound SIP calling through a Twilio trunk. LiveKit successfully creates sessions and SIP participants, but no actual SIP INVITE reaches Twilio. ## Symptoms 1. ✅ Notification worker successfully creates LiveKit room 2. ✅ Worker calls

create_sip_participant()

- returns success 3. ✅ Session appears in LiveKit dashboard (Telephony → Sessions) 4. ✅ Session shows 1 participant with SIP feature 5. ❌ No SIP INVITE reaches Twilio (checked Twilio debugger - no entries) 6. ❌ No call appears in LiveKit Calls log 7. ❌ No actual phone call occurs ## What I've Tried 1. ***Credential authentication*** - Matching credentials between LiveKit trunk and Twilio credential list 2. ***IP-only authentication*** - Using IP ACL with

0.0.0.0/0

3. ***Various address formats:*** -

<http://XXX.pstn.twilio.com|XXX.pstn.twilio.com>

-

<http://sip.twilio.com|sip.twilio.com>

-

sip:XXX.<http://pstn.twilio.com|pstn.twilio.com>

4. ***Verified:*** - Phone number is assigned to Twilio trunk - Termination settings are correct - Credentials match exactly - Trunk ID in code matches LiveKit dashboard ## Error in LiveKit Calls Log (when entries appear) After ~1 hour delay, calls show in LiveKit Calls log with: FAILED - unexpected status from INVITE response: sip status: 403: Forbidden However, these same calls ***never appear in Twilio's debugger***, suggesting the SIP INVITE isn't reaching Twilio at all, or is being rejected before Twilio logs it. Returns success with SIP Call ID, but no actual call is made. ## Questions 1. ***Is there a known issue with Twilio trunks in the US East B region?* 2. ***Are there additional trunk configuration parameters required for Twilio that aren't in the standard API?* 3. ***Can you check the SIP logs for trunk to see what's happening with the INVITE?* 4. ***Is there a firewall or network issue preventing LiveKit from reaching Twilio's SIP endpoint?* 5. ***Could this be related to the trunk being created via API vs dashboard?* ## Additional Information - Using LiveKit Python SDK (livekit-api) - Notification agent successfully joins rooms via dispatch rules - Inbound SIP calling to LiveKit works fine (using a separate inbound trunk) - This is for an outbound notification system - automated calls to notify customer Any assistance would be greatly appreciated. Thank you!

Hi Michael, thank you for the very detailed issue description! It sounds like you are using Livekit Cloud. Would you be able to provide some details to help with diagnostics? For example, project ids, calls ids, etc.

Hi Alex I apologize yes it is LiveKit Cloud but I was able to resolve the issue. It seems I was using the incorrect address and I needed to remove the IP Access Controls from the Twilio Trunk settings and just use Credentials. Once I got those settings set correctly the call was executed properly Thanks Mike