Hi team, we need your help to investigate an issue we’re facing today with our outbound campaigns. We’re seeing a much higher number of failed calls compared to yesterday. The calls are ending with the status: call.in-progress.error-sip-telephony-provider-failed-to-connect-call We’re running thousands of calls today, just like we did yesterday. While we saw a few of these errors yesterday, today it has increased significantly, reaching hundreds of failures. Here are some example call IDs to help with the investigation:

b7fde20e-6b86-4aec-8562-80581a2a97b1  
327e09ac-4f88-4120-be5f-454dbbf0f4e5  
6e25c347-3448-40fd-ad69-0e0e32982794  
0ee74c68-def2-437a-b22e-648aa9725341  
c26fe3a3-6b2d-4fe8-8abf-39dc06497394  
c3d3ee2c-e905-4cc4-88db-bb38a5c1299c  
7f528659-3b2d-47e3-bb7c-05996057d344  
dd2f7fdb-36a6-4b26-a538-d64d2707c1b9  
6bcd5847-fc73-4790-be1e-9a0a5ed7c538  
41cc8c6f-d289-458a-b616-654f5b1cc58e

We’re also checking things on our end with our SIP trunk provider, but any help or insight from your side would be greatly appreciated. Thanks in advance!

Thank you for sharing these details and the example call IDs. I understand how urgent and disruptive a spike in SIP call failures can be, especially during high-volume campaigns. While I don't have specific information available right now to pinpoint the cause of the "call.in-progress.error-sip-telephony-provider-failed-to-connect-call" error, your proactive approach in checking with your SIP trunk provider is a good step. If there are any changes or patterns you notice, feel free to share more details, and I'll do my best to assist further.

Hey! To help track down this issue, could you share: - 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!

Hey, This issue has been occurring at various times throughout the day, and we’ve been noticing it with increasing frequency. As requested, here are the timestamps for some of the call IDs we previously shared: b7fde20e-6b86-4aec-8562-80581a2a97b1 — 2025-05-13T14:57:55.686Z 327e09ac-4f88-4120-be5f-454dbbf0f4e5 — 2025-05-13T14:57:54.923Z 6e25c347-3448-40fd-ad69-0e0e32982794 — 2025-05-13T14:57:54.560Z The expected behavior was for the calls to successfully connect. However, instead of that, we’re getting the following error status: call.in-progress.error-sip-telephony-provider-failed-to-connect-call Since this error is occurring more frequently and now affecting hundreds of calls, we’d really appreciate your help in identifying the root cause.

@Shubham Bajaj We spoke with our telephony provider and re-traced the numerous calls that are having this error. What we discovered is that these calls are not reaching their network, meaning it’s likely a problem on Vapi's side. It’s worth noting that these mass cases started just a few days ago, and they mostly happen on the first call attempt, because if we redial, the call goes through. However, we would like this to be investigated and resolved.

Whether you are using Dashboard or API for config, please follow this guide on SIP trunking:

and @Shubham Bajaj We've already reviewed the documentation, and the implementation is correct — the issue is not on our side. Another point is that our telephony provider investigated several of the calls showing this error and confirmed that they never reached them. This started happening recently, even though we haven't changed anything in our code

Given your SIP trunk provider confirms the calls are not reaching them and your configuration hasn't changed, the most actionable next step is to escalate this to Vapi support with detailed evidence. Please open a support ticket and include: - A list of affected call IDs and their timestamps - Confirmation from your provider that the calls are not received - A brief summary of your SIP trunk configuration This will help the Vapi team investigate backend logs and identify any platform-side issues. For reference, see the [Vapi SIP trunking guide](https://docs.vapi.ai/advanced/sip/sip-trunk) and [call end reasons](https://docs.vapi.ai/calls/call-ended-reason). Sources: - [Vapi SIP trunking guide](https://docs.vapi.ai/advanced/sip/sip-trunk) - [Vapi call end reasons](https://docs.vapi.ai/calls/call-ended-reason)