> ## Documentation Index
> Fetch the complete documentation index at: https://docs.neuro-tech.io/llms.txt
> Use this file to discover all available pages before exploring further.

# Troubleshoot Quick Login

> Resolve QR, event connection, callback, and session problems

Find the stage that failed before starting another attempt. A successful QR response confirms request creation, not identity approval or application login.

| Symptom                                        | What to check                                                                                                                                            |
| ---------------------------------------------- | -------------------------------------------------------------------------------------------------------------------------------------------------------- |
| QR request fails                               | Confirm HTTPS, the Neuron host, `/QuickLogin` availability, JSON content type, and all four required request fields. Inspect the actual HTTP status.     |
| Browser reports a CORS error                   | The Neuron must allow your page origin, POST, and `Content-Type`. Adding headers to your own page cannot change the Neuron's CORS policy.                |
| WebSocket fails                                | Check `wss://<host>/ClientEventsWS`, subprotocol `ls`, allowed origins, and network/proxy WebSocket support.                                             |
| QR appears but no result arrives               | Register the event connection first and use that exact tab identifier in the QR request. Confirm the user approved and that the connection remains open. |
| App refuses a code                             | Start a fresh attempt; codes expire after five minutes. Check the app's supported provider, identity status, and displayed purpose.                      |
| Clicking the QR does nothing                   | Open on a device with a compatible identity app, or scan from another device.                                                                            |
| Callback is never reached                      | Check callback HTTPS reachability, the service registration's five-minute lifetime, and whether the QR request contains the correct `serviceId`.         |
| Callback completed but the browser still waits | Return valid JSON, even `null`, from the callback. Check `SignatureReceivedBE` delivery and query your backend's session state.                          |
| Backend says the attempt is unknown            | Match callback `SessionId` to the original registration's `sessionId`, including case. Reject expired or reused attempts.                                |
| Agent API exchange fails after approval        | Browser-only mode does not establish a Neuron session. Use session mode, preserve cookies, and check the account prerequisites.                          |
| Embedded reference script crashes or redirects | The deployed script depends on its example page's filter controls and includes a five-minute redirect. Adapt it to your page lifecycle.                  |

## Expiry, cancellation, and retries

Stop refresh timers and close event connections after completion, cancellation, or navigation. Abort pending requests so a late QR response cannot replace a completed result. Use a fresh unpredictable tab identifier for a new attempt, and ignore responses belonging to previous attempts.

Closing a tab does not revoke an issued QR. Do not assume the service sends an explicit rejection or cancellation event: the public guide documents success events. Provide a visible waiting state, cancel action, timeout, and retry action in your application.

## Session-specific checks

Browser-only requests can work without cookies. Session and session-proxy modes require them. Check cookie storage, SameSite and Secure attributes, credentialed CORS, and whether browser privacy settings block cross-site cookies. A proxy must retain a cookie jar for the Neuron session and bind it to the correct application user.

## Diagnose without exposing identities

Record the stage, status code, timing, and connection state. Avoid logging full identity results, QR signing URLs, attachment access URLs, cookies, or tokens. When reporting a provider issue, send a redacted request shape and the exact endpoint and event type involved.

Compare with the [provider-hosted example](https://eu.quicklog.in/QuickLogin.md) to distinguish your integration's origin or lifecycle problems from service availability.