Hi @droganov,
Welcome to the Auth0 Community!
What is the value of APP_BASE_URL in the Vercel Environment Variables? Is it set to http://localhost:3000? If so, this is likely the issue. The APP_BASE_URL in Vercel needs to be your Vercel domain. For example, YOUR_VERCEL_DOMAIN.vercel.app.
Here is a guide on deploying Next.js apps with Auth0 to Vercel: How to Deploy a Next.js App Secured By Auth0 to Vercel
I would also recommend submitting feedback about improvements to error messages. You can follow this article regarding feedback: How to Submit Product Feedback or Feature Requests
Best,
Mary Beth