I am experiencing an issue with inbound calls on VAPI. When I first configure the phone number and SIP credentials, everything works correctly — inbound calls are received without problems. However, after some time, inbound calls fail and the caller only hears a busy tone, as if the SIP account is no longer connected. Despite this, outbound calls continue to work normally. Could you please investigate why the SIP registration seems to expire or disconnect for inbound calls, while outbound functionality remains active? Number ID: 561d2b1b-607e-4ff9-95ce-fbe0fe74619c

Thank you for the details. To help investigate further, could you please confirm which SIP provider you are using and whether you have configured any registration/keepalive intervals or allowlisted the required Vapi SIP signaling IPs for inbound calls? This will help narrow down potential causes for the inbound registration issue. Source: - [Vapi SIP Trunking Documentation](https://docs.vapi.ai/advanced/sip/sip-trunk)

I am currently using Vono as my SIP provider. Since it was not working properly with the domain vono2.me, I configured it directly using the IP address. At the moment, I have not set up any KeepAlive configuration in Vapi, nor have I added the Vapi SIP signaling IPs to an allowlist. I can check with my SIP provider about the possibility of allowlisting these IPs. Even though the connection works for a while, could the missing allowlist configuration still be affecting inbound call registration?

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!

Since the SIP is no longer connected, there is no call ID generated when the issue occurs — I only receive a busy tone. However, the call ID of the last successful call was 019997cd-f9ec-7889-9d85-2665b3aef2e9.

We apologize for the delay in responses lately. We are in process of making some changes to our workflow in how we handle support requests. The good news is that we are starting to get back on track of having a 48 hour response time and we would like to start cleaning up anything old. With that being said, just wanted to check in with you to see if you have made any progress or changes to your project since support has last reached out.

No. May you help me? I really liked the platform, the SIP connection problem is my only issue, but without it I can’t go any further.

Hi there, Thanks for the details! Just checking — is there any chance you could try configuring Twilio as your SIP provider? It’s the most fully supported and stable option on our platform, and using it would help us better isolate whether the issue is related to the SIP configuration or the provider itself. Let me know if that’s possible, and I can guide you through the setup. Best, Kyle Vapi Support

It does work fine with Twilio, but it doesn’t meet my needs.

There was a fix for auto-disconnecting SIP trunks recently so you might want to try out your other telephony provider to see if it works.