Investigation Request: Prolonged SIP Registration Failure for Trunk ID: 74c2e0b3-b2b6-4b9b-ad79-939a2487434e Hi Vapi Team, I am writing to request an urgent investigation into a prolonged SIP registration failure for one of my BYO SIP trunks. The service was down for over 48 hours because no REGISTER requests were sent from your platform. Here are the details of the trunk: SIP Trunk Name: Opennet Credential ID: 74c2e0b3-b2b6-4b9b-ad79-939a2487434e Authentication Username: 3652541346 Please see the timeline of the issue below. All times are in GMT+1 (Central European Time). Last Successful Registration: The last successful REGISTER was sent by Vapi on November 8, 2025, at approximately 05:00 GMT+1. Start of Failure: From approximately 06:00 GMT+1 on November 8, 2025, your system stopped sending REGISTER requests to our provider. Service Restored: The registration was only re-established when your system sent a new REGISTER request on November 10, 2025, at approximately 09:25 GMT+1. We have confirmed with our provider (Opennet) that they did not receive any REGISTER or OPTIONS keep-alive requests from Vapi's IP addresses (44.229.228.186, 44.238.177.138) during this entire outage period. This strongly suggests the issue originated within the Vapi platform. Could you please investigate your outbound logs for this trunk and provide information on why your system stopped sending registration and keep-alive requests for over two days? Thank you for your help in resolving this matter. Best regards,

Hi nytms, If you're experiencing issues with call forwarding drops, you can follow the troubleshooting steps outlined in the [Debug call forwarding drops guide](https://docs.vapi.ai/phone-calling/transfer-calls/debug-forwarding-drops). Here is a quick overview of some of the steps you can take: 1. **Verify Forwarding Initiation**: Check if Vapi successfully initiated the forwarding by examining the

endedReason

. If it shows

"assistant-forwarded-call"

, proceed to check your telephony provider logs. 2. **Check Configuration**: Ensure your assistant settings are correct. The

serverMessages

configuration should not contain

"phone-call-control"

, and the

phoneCallProviderBypassEnabled

should be set to

false

unless you are using custom call control logic. 3. **Review Telephony Provider Logs**: Use the

phoneCallProviderId

from the Vapi call object to trace the call in your provider's dashboard and look for any transfer errors. 4. **Analyze SIP Packets**: If SIP trunking is involved, review the SIP signaling using Wireshark to check for missing or error-prone REFER packets. Ensure all configurations match your call transfer requirements and reviewed steps have been accounted for. If you need any more specific help, feel free to ask.