Call ID: 019eabef-ff3c-7000-9569-553baecfe3a9 Timestamp: 2026-06-09 at 10:31 UTC Expected response: Outbound phone call connects and rings the destination number via Telnyx BYO SIP trunk. Actual response: Call goes to status "queued" but never connects. Error: call.in-progress.error-sip-outbound-call-failed-to-connect. No SIP traffic reaches Telnyx — no CDR logs appear on their side at all. Additional details: Provider: byo-sip-trunk (Telnyx FQDN, gateways 192.76.120.10 / 64.16.250.10, outbound only, options ping enabled, SIP registration realm sip.telnyx.com) All Telnyx-side configuration verified: number assigned to SIP trunk, trunk assigned to Outbound Voice Profile, destination country enabled. Direct Telnyx number import via dashboard also failed consistently with "Incorrect Telnyx Credential" errors before switching to BYO SIP trunk approach.

That sounds frustrating, especially since the call never appears to leave Vapi. If Telnyx shows no SIP traffic or CDRs at all, it suggests the failure may be occurring before the INVITE is even sent to your BYO SIP trunk. Have you checked whether Vapi is successfully resolving and routing to the Telnyx FQDN, and whether there are any SIP trunk validation or transport-related errors in the Vapi logs for this Call ID? @Splend1d

Thanks for the quick response. I cant see no SIP traffic reaches Telnyx at all. In the call logs I only see "call.in progress.error sip outbound call failed to connect" as the ended reason. There are no further details visible in the dashboard. Is there a way to access more detailed SIP-level logs or transport error logs for a specific Call ID?

Thanks for the info, this actually makes the issue clearer. If Telnyx isn’t seeing any SIP traffic at all, then the failure is happening before the INVITE even leaves Vapi. The standard call logs only show that high-level “failed to connect” message, so they won’t give much more detail. You’ll need SIP/debug (ladder) logs for that specific call to see what’s happening on the transport side. By the way, are you running the BYO trunk over UDP, TCP, or TLS? @Splend1d

Hi, Thanks for the detailed report. I've looked at the logs for your org and can confirm what's happening at the SIP layer. Vapi's SBC is successfully sending the SIP INVITE to Telnyx's gateway (192.76.120.10). The issue is that Telnyx responds with SIP 404: Not Found within about 300ms, before the call can progress. This happens at the SIP routing level, which is why no CDR appears on Telnyx's side. Telnyx only generates CDRs for calls that reach the ring/answer stage, not for ones rejected at the signaling layer. The destination you're calling (+48, Poland) is the key detail. Telnyx's Call Control Applications have an "Allowed Destinations" setting that defaults to North America only, and this is independent of your Outbound Voice Profile settings. Even if your Outbound Voice Profile has Poland enabled, the Call Control Application can still block the call with a 404 at the routing step. Here is what to check and fix: In Telnyx portal, go to Voice > Call Control Applications > open the application linked to your SIP trunk. Look for an "Allowed Destinations" or "Permissions" section and add Poland (or set it to allow international / worldwide). Also verify that your Outbound Voice Profile has Poland enabled under international calling destinations. One important heads-up: if you make changes to the Call Control Application and it ends up generating a new Application ID (this can happen depending on how the change is made), you would need to recreate or update your BYO SIP credential in Vapi to reference the new Application ID. On the "Incorrect Telnyx Credential" errors you saw when trying the native Telnyx number import: that is a separate issue from the BYO trunk setup, and it does not affect your SIP trunk calls. If you want to revisit native Telnyx number import separately, I am happy to help with that. Try the Call Control Application change first and let me know if calls to +48 start connecting. I expect that to resolve it.

I'm unable to find anything called "Call Control Applications" in my Telnyx portal. I'm using a SIP trunk with FQDN type connection. Either way, every place i could find something related to Allowed destinations (in the Outbound Voice settings and SIP connection settings, i have made sure that Denmark is. Also worth noting, the destination number is actually Denmark (+45), not Poland (+48), in case that changes anything. Still no success.

Since you're using a Telnyx FQDN SIP trunk over UDP and Telnyx isn't seeing any inbound SIP traffic or generating CDRs, I'd focus less on the destination country at this point and more on the handoff between Vapi and the trunk itself. The key signal here is that the call never appears to reach Telnyx. I'd verify the exact FQDN configured in Vapi, confirm that Telnyx is accepting traffic from the source IPs Vapi is using, and see if Vapi support can pull backend SIP traces for that Call ID. If the INVITE isn't leaving Vapi, the issue is likely upstream of Telnyx. Have you been able to test the same Telnyx trunk from another SIP client or provider to confirm it's accepting outbound traffic successfully over UDP? @Splend1d

Hi, Good news from the logs, your trunk is actually working. We can see calls to South Africa (+27) connecting successfully through the same BYO SIP trunk, which rules out any FQDN or signaling-layer issue on Vapi's side. The SIP 404 errors are isolated to a specific destination: +48607183278, which is a Polish number (+48 country code). Every single failing call attempt from your org is going to that number. I don't see any calls to a +45 (Denmark) number in the logs at all, so it's possible there's a mismatch between what you expected to be dialed and what's actually being sent. Two things to check: Confirm the number you're trying to reach. The failing destination in Vapi's logs is consistently +48607183278 (Poland), not a Denmark number. If you have a campaign or test set up with that number, that's the one to focus on. In your Telnyx Outbound Voice Profile, check that Poland (+48 / PL) is enabled as a destination. South Africa is enabled and working, so the profile itself is active - Poland may simply not be toggled on. This would produce exactly the SIP 404 pattern we're seeing: quick rejection at the routing layer, no CDR generated on Telnyx's side. Once Poland is enabled in the Outbound Voice Profile, I'd expect those calls to connect without any other changes.

I have definatly not made any attemts to call South Africa, and not Poland. Are you sure it is the right log files you have been looking at?

Hey, You're right to question that, and I owe you a straight answer: I was looking at the wrong data. The calls to South Africa and Poland belonged to other Vapi customers, not your account. An error in how I correlated the logs caused me to pull traffic from unrelated accounts and present it as yours. I apologize for the confusion that caused. That Zoiper test is exactly the right call - SIP 503 "No Routes Found" from an independent client confirms the issue is in Telnyx's routing configuration, not in Vapi or your BYO SIP credential setup. Telnyx support should be able to identify what's missing on their end, whether that's an outbound route, a missing profile assignment, or a destination permission. Please do update this thread once Telnyx sorts it out. Happy to help verify things on the Vapi side once the trunk is routing correctly.

@Jarrah The issue has been resolved. Some org-level restrictions on Telnyx's part was the culpit. Thank you for your help, directing me towards a resolution.