Telnyx FQDN SIP trunk inbound calls rejected with Q.850 cause 17 - never appears in Call History

Support Help
1

Hi Retell team,

Inbound calls to my Telnyx number are being rejected with Q.850 cause code 17 (SIP 486 User Busy). The calls never appear in Retell Call History.

Setup:

  • Workspace: info@infiniscopecs.com
  • Number: +15715970123 (imported as Custom Telephony)
  • Telnyx connection type: FQDN
  • FQDN added: sip.retellai.com, port 5060, type A
  • SIP subdomain: infiniscope-salon-ai.sip.telnyx. com
  • Termination URI in Retell: infiniscope-salon-ai.sip.telnyx. com
  • Inbound agent: assigned and published
  • Transport: TCP

What happens:

  • Telnyx CDR confirms inbound INVITE is sent to Retell
  • Retell returns 486 User Busy immediately
  • Call duration: 0 seconds
  • Call never appears in Retell Call History

I have tried deleting and re-importing the number multiple times. Outbound from Retell works fine.

Please advise.

2

Hi @info25

The FQDN’s DNS record type should be SRV, not A. That’s likely why inbound is failing.Add sip.retellai.com as an SRV record (not A).

You can see the full Details at (Telnyx - Retell AI)

Thank You