Outbound fails with telephony_provider_permission_denied — custom Twilio SIP trunk, inbound works

Support Help
1

Workspace: call and close
Number: +18172007666 (Custom telephony)
Agent: Marcus, agent_7c8c91b984b7a2b42986ece7ec

Inbound works perfectly on this trunk — calls connect, transcripts and
recordings are produced, webhooks fire.

Outbound fails on every attempt: 0:00 duration, $0.000 cost, not_connected,
“telephony_provider_permission_denied”.

Failed call IDs:
call_c696ec04be98617498fc7ade775
call_069a7c8d472ceee0eb450151284

Already ruled out:

  1. Fails from Retell’s own “Make an outbound call” button, not just the API.
  2. Fails when dialling Twilio’s own trunk test number +1 812 389 4546, so it is
    not destination-specific.
  3. Twilio trunk TK7aa6e05f51cbf3ab905caf196974707d:
    • Termination URI callandclose.pstn.twilio.com, US1 routing active
    • IP ACL “Retell SBC” containing 18.98.16.120/30, attached to Termination
    • Credential list “callandclose” attached to Termination
    • Credential username is “callandclose1” (Twilio appended the 1); this exact
      value is set as SIP Trunk User Name in Retell, password re-entered on both
      sides
    • +18172007666 assigned to the trunk
  4. Twilio account active, in credit. Outbound Transport TCP.

Per /t/enable-outbound-calling-custom-telephony-twilio-sip-trunk/2525 the same
symptom was diagnosed by packet capture. Please run one on those call IDs, or
enable outbound on this account if that is what is gating it.

2

Hey @realmvphomes Thanks for sharing the Call IDs. I’ll check them with the team and get back to you as soon as I have an update.

Thank You

3

Hello @realmvphomes

I pulled the SIP trace for call_c696ec04be98617498fc7ade775:

  • Your trunk challenges our INVITE with 407 Proxy Authentication Required, we respond with digest auth for user callandclose1, and your trunk then returns SIP/2.0 403 Forbidden with X-Twilio-Error: 32202 Authentication failure - bad user credentials.
  • Our INVITE egressed from 18.98.16.122 (inside the 18.98.16.120/30 allowlist you already added), and the 407 successfully fired — so IP ACL, Geo Permissions, and caller-ID binding are all cleared. 32202 is specifically a Credential List password mismatch.

To fix:

  1. In Twilio Console → Elastic SIP Trunking → your trunk (TK7aa6e05f51cbf3ab905caf196974707d) → Termination, confirm the callandclose Credential List is the one attached to Termination Authentication (not a sibling trunk).
  2. Open user callandclose1 in that Credential List and set a brand-new password. Don’t rely on a “confirm” view — Twilio never displays the stored value, so it can’t verify a match.
  3. Copy the new password character-for-character into the SIP password field on the Retell phone number for +18172007666, and save.

Thank You