---
"@context": https://schema.org
"@type": TechArticle
"@id": https://www.twilio.com/docs/api/errors/80905#article
headline: "80905: Unknown Scenario"
url: https://www.twilio.com/docs/api/errors/80905
inLanguage: en
dateModified: 2026-06-08T12:04:59.000Z
author:
  "@type": Organization
  name: Twilio Developer Education Team
publisher:
  "@type": Organization
  name: Twilio
---

# 80905: Unknown Scenario

Log Level: WARNING

## Description

This warning appears when Twilio Proxy receives an inbound call or message on a Proxy number, but cannot route the interaction through a valid Session. Proxy handles masked communications through Sessions that map two Participants. If the inbound traffic arrives for a closed or non-existent Session, configure `out_of_session_callback_url` to return valid TwiML or valid auto-create session JSON so Proxy can continue handling the interaction.

### Possible causes

* The inbound caller or sender is not a Participant in an open Session for the Proxy number that received the interaction.
* The matching Session has already closed, expired because of `ttl` or `dateExpiry`, or was deleted.
* The Proxy Service does not have `out_of_session_callback_url` configured, so inbound traffic for a closed or non-existent Session has no fallback handling path.
* The `out_of_session_callback_url` response is not valid TwiML with `Content-Type: application/xml` or valid auto-create session JSON with `Content-Type: application/json`.
* The Session or Participant configuration does not match the expected `identifier` and `proxyIdentifier` pairing for the inbound interaction.

### Possible solutions

* Confirm that the inbound call or message is reaching the correct Proxy Service and a Proxy number assigned to that Service.
* Verify that the caller or sender is a Participant in an open Session for that Proxy number.
* If the original Session has closed or expired, create a new Session for the participants before expecting Proxy to forward additional calls or messages.
* Configure `out_of_session_callback_url` on the Service if you need to handle inbound traffic that arrives after a Session closes or when no Session exists.
* Make sure your out-of-session webhook returns valid TwiML for voice or messaging, or valid auto-create session JSON if you want Proxy to create a new Session automatically.
* Review your Session `ttl`, `dateExpiry`, Participant `identifier`, and `proxyIdentifier` values so the Session stays active for the expected duration and the inbound interaction can be matched correctly.

#### Additional resources

* [Proxy: One-to-one Masked Communications](/docs/proxy)
* [Service resource](/docs/proxy/api/service)
* [Out-of-Session Callback Response Guide](/docs/proxy/out-session-callback-response-guide)