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

Support Help
1

Hi team,

I’ve been trying to connect my Telnyx number to Retell AI via SIP
trunking but inbound calls are consistently rejected.

Workspace: jack kuan Workspace
Number: +16047429464 (Telnyx, Canadian number)
Agent: Bespoke Receptionist (published)

My configuration:

  • Connection type: FQDN, SRV, TCP
  • Inbound SIP transport: TCP
  • Number imported as custom telephony
  • Inbound agent assigned

What happens:

  • Telnyx Debug logs confirm 16+ inbound call attempts received
  • All rejected with Q.850 cause code 17
  • Calls never appear in Retell Call History
  • Retell billing shows 0 call minutes

Could someone please check if my inbound SIP routing needs to be reset?

Thank you!

2

Hello @jack5538957

Can you share the PCAP file for these calls

Thank you.

3

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Hi Omar,

Thanks for your reply.

I wasn’t able to locate a PCAP download option in the Telnyx debugging interface, but I’ve attached a screenshot of the failed calls for reference.

All inbound calls appear to reach Telnyx successfully, but they are immediately rejected with Q.850 cause code 17 and 0 second duration. The calls also do not appear in Retell Call History.

Example Telnyx Call IDs:

  • 891b61b8-19cb-11f1-ba43-02420aefd81f
  • a8683636-1804-11f1-a099-02420aef26a0

Configuration summary:

  • Provider: Telnyx (SIP connection)
  • FQDN: sip.retellai.com:5060
  • Transport: UDP
  • Destination number format: E.164
  • Phone number: +16047429464
  • Retell provider: Custom telephony
  • Inbound agent: Bespoke Receptionist/V6

Please let me know if you need any additional information from my side.

Thank

image
image3140×1294 254 KB

4

image
image3130×1324 337 KB

here is another half,thx

5

Hello Jack,

Unfortunately, I still need the PCAP files to identify the issue. Could you please contact their support team to request the PCAP files? Thank you.

6

Hello,

I am testing a SIP trunk integration with Telnyx.

Telnyx support investigated a failed call and reported the following error:

486 Busy Here D61 – which indicates that the user portal level does not allow this type of inbound SIP call.

My Retell phone number:
+1 604 742 9464

Telnyx Call ID:
891b61b8-19cb-11f1-ba43-02420aefd81f

Telnyx confirmed the SIP INVITE reached Retell but was rejected.

Could you please confirm if inbound SIP calls are disabled for trial accounts?

If so, is it possible to enable SIP inbound temporarily for testing?

Thank you.

7

Hello Jack,

Here is what code 61 means:

image-18eb3086.png
image-18eb3086.png1473×380 45.9 KB

You will need to upgrade your Telnyx account, as they are currently blocking the calls not us.