---
"@context": https://schema.org
"@type": TechArticle
"@id": https://www.twilio.com/docs/api/errors/60517#article
headline: "60517: SNA User-Agent Mismatch Error"
url: https://www.twilio.com/docs/api/errors/60517
inLanguage: en
dateModified: 2026-06-08T12:04:59.000Z
author:
  "@type": Organization
  name: Twilio Developer Education Team
publisher:
  "@type": Organization
  name: Twilio
---

# 60517: SNA User-Agent Mismatch Error

Log Type: TWILIO

Log Level: ERROR

## Description

This error occurs when a Verify Silent Network Auth verification reaches the redirect stage, but Twilio detects a `User-Agent` mismatch before the SNA flow can complete. To use SNA, start the verification with the `sna` channel, invoke `sna.url` from the client device on a mobile network, and complete the flow before checking the verification result.

### Possible causes

* A `User-Agent` mismatch was detected during one or more redirects in the SNA flow.
* The SNA request started in one client context and continued in another, such as moving between a mobile app and a mobile browser during redirects. This can change the `User-Agent` and cause the verification attempt to fail.
* The implementation did not keep a consistent client context while following the carrier redirect chain. Some carriers require multiple redirects before you can complete the SNA flow.

### Possible solutions

* Retry the verification using another Verify channel for this end user, such as SMS. For SNA errors in general, you can fail over to SMS or another verification channel except for 60540.
* Invoke `sna.url` directly from the end user's mobile device that is connected to the mobile network, then complete the verification with a server-to-server Verification Check request.
* Follow all redirects returned during the SNA URL invocation. Some carriers use multiple redirects in the SNA flow.
* If you implement SNA in a mobile app, keep the request in a single client context during the redirect flow instead of switching between app and browser experiences.
* If you want SNA with built-in SMS fallback, use `channel=auto` so Verify can attempt SNA first and fall back to SMS when needed.

#### Additional resources

* [Verify Silent Network Auth overview](/docs/verify/sna)
* [Verifications API reference](/docs/verify/api/verification)
* [Best practices for Verify SNA error handling](/docs/verify/best-practices-for-verify-sna-error-handling)