When I try to call from my voip cli, it goes into voicemail and I can hear the voicemail, but on vapi it just gives me this message. "An error occurred in this call: call.in-progress.error-sip-telephony-provider-failed-to-connect-call" call id 94acd47e-b5f2-40ce-8f33-71b92ec4085a 27.05.2025 11:07:18 44xxxxxxxx 39xxxxxxxxx Italy OMNITEL - mobile no answer €0.033 00:00:00 €0

The error

call.in-progress.error-sip-telephony-provider-failed-to-connect-call

means Vapi could not connect the call through your SIP provider. A common cause is a misconfigured SIP trunk or missing network allowlist. Please double-check that your SIP provider is correctly configured in Vapi and that you have allowlisted the required Vapi IPs (e.g.,

44.229.228.186/32

,

44.238.177.138/32

). Here’s a quick checklist:

markdown
- Verify SIP trunk credentials (username/password or IP-based)
- Ensure your SIP provider is routing calls to the correct Vapi SIP URI
- Allowlist Vapi's IPs in your firewall/SIP provider settings

If the issue persists, review your SIP trunk logs for authentication or routing errors. Sources: - [Vapi Call Ended Reasons](https://docs.vapi.ai/calls/call-ended-reason) - [Vapi SIP Trunking Setup](https://docs.vapi.ai/advanced/sip/sip-trunk)

I am using zadarma and some calls are fine, it goes through but a very high percentage are not going through.

Suggestion: Double-check that both Vapi IPs are allowlisted in your Zadarma account and any relevant firewalls, as missing or partial allowlisting can cause intermittent call failures. Example (Zadarma External Server settings):

External server (SIP URI): YOUR_VIRTUAL_NUMBER@sip.vapi.ai
Allowlist IPs: 44.229.228.186/32, 44.238.177.138/32

After updating, test several calls to confirm improved reliability. [See full Zadarma integration steps](https://docs.vapi.ai/advanced/sip/zadarma) Sources: - [Vapi SIP Trunking Setup](https://docs.vapi.ai/advanced/sip/sip-trunk) - [Vapi Call Ended Reasons](https://docs.vapi.ai/calls/call-ended-reason) - [Zadarma SIP Integration](https://docs.vapi.ai/advanced/sip/zadarma)

Message marked as helpful by @! AetherMind! 🎉

checking if this is resolved/solved for you?

@mayseamsberry Is the problem solved? If it is still there, let me know. I can perhaps help you with it.

@Subrat Sagar it is okay now

Great to know.

Glad the issue was resolved. Please reach out to us if you have any other questions regarding this issue

hello can you resend my magic link

Are you having trouble logging in? Please provide the email address associated with the account and I will fix it

@Subrat Sagar I am having issues with concurrency, i have no active calls at the moment and it won't let me start a new call.

Hey, could you check again? I sent you the magic link.