Diagnose this browser or API failure without weakening security controls.

Inspect the browser console and network request, URL, method, status, redirect chain, request and response headers with credentials redacted, CORS behavior, cookies, CSRF handling, token audience and expiration metadata without token contents, backend logs, and route authorization.

Distinguish authentication failure, authorization denial, malformed request, expired session, CORS rejection, CSRF rejection, incorrect endpoint, DNS or TLS failure, backend exception, and user-interface rendering failure. Explain why the returned status code and message are or are not appropriate.

Do not disable authentication, CORS, CSRF, TLS verification, or permission checks as a diagnostic shortcut. Propose the smallest correction and the allowed-path and denied-path tests required before implementation.