Next app deployed on vercel - [CallbackHandlerError]: Callback handler failed. CAUSE: access_denied (Unauthorized)

[dawid.matuszczyk]

Hi @bryso

Welcome to the Auth0 Community!

Thank you for posting your question. As your application is working properly locally, the issue may be connected to the Vercel caching mechanism.

We have an excellent Knowledge Solution regarding this issue, which you can find here

Callback handler fail 400 Bad request with NextJS

Problem statement After a successful login with the Next.js SDK, when redirected to the callback route /api/auth/callback, a 400 Bad Response error occurs. Symptoms The /api/auth/callback is showing a Chrome error “net::ERR_HTTP_RESPONSE_CODE_FAILURE” a few milliseconds after, so a timeout is discarded. LoginHandlerError: Login handler failed. CallbackHandlerError: Callback handler failed. 400 Bad request Steps to reproduce Go to the unauthenticated page Login Troubleshooting Check if the e…

Thanks
Dawid