I have a call transfer tool transfering calls to a sip destination. The SIP uri destination is always the same. It works on Tuesday and stop working on Wednesday. I don't understand what is happening. The call doesn't arrive to the virtual PBX destination

Check if your SIP system is properly configured to handle SIP REFER messages, as VAPI uses this method for transfers. According to [Discord discussions](https://discord.com/channels/1211482211119796234/1333747605628391434), compatibility issues with SIP REFER handling are a common cause of sudden transfer failures. Try these troubleshooting steps: 1. Review firewall settings - ensure SIP ALG isn't interfering with messages 2. Check logs for any "No destination" validation errors 3. If using Twilio, try changing the routing region to US Sources: - [Discord discussion about SIP REFER handling](https://discord.com/channels/1211482211119796234/1333747605628391434) - [Discord discussion about firewall issues](https://discord.com/channels/1211482211119796234/1334919245468799007) - [Discord discussion about Twilio routing](https://discord.com/channels/1211482211119796234/1337685081287954546)

it doesn't work now

Hey! To help track down this issue, could you share: - The call ID This would really help us figure out what went wrong!

sure, I am going to try again as soon as possible

🔵 14:11:15:010 Using tool.destinations\[0\]: { "type": "sip", "sipUri": "sip:[502@tecxxxs.vpbx.me](502@tech2call-cibernos.vpbx.me)", "message": "Su llaxxxx retire.", "description": "Utiliza xxxxdique.", "transferPlan": { "mode": "warm-transfer-wait-for-operator-to-speak-first-and-then-say-message", "message": "Hola", "sipVerb": "refer" } } 🔵 14:11:15:020 Live Call Manager Ending...(assistant-forwarded-call) The call was forwarded successfully, can you ask your telephony for PCAP file so I can take a look into and confirm what's not working for your telephony.

I have not receiving nothing in the SIP destination

Hello Luis, Could you please share your telephony side of the PCAP file and the call logs so that we can double-check our side? Our logs and PCAP file indicate that the call was transferred. Please let me know your thoughts on this matter.

I can't capture nothing in our side because we are not receiving nothing

Hey, Could you please schedule a brief call at your convenience so we can discuss this matter in detail? Kindly use the following link to book a suitable time: .

Hi! I’ve booked the meeting as requested. However, the scheduled time falls outside our working hours, so I won’t be able to take traffic captures during that period. That said, I can share my configuration to help troubleshoot the issue. Would that work for you?

Hey! To help track down this issue, could you share: - The call ID - When exactly this happened (the timestamp) - What response you expected to get - What response you actually got instead This would really help us figure out what went wrong!

Thank you very much for your help in the call. Problem solved!

Marking this ticket as Solved ✅