The provided information is not sufficient for a definitive response, but one possibility is that you are requesting API authorization (audience parameter) and consent is required because it won’t be skipped for localhost (https://auth0.com/docs/api-auth/user-consent#skipping-consent-for-first-party-applications).
Since consent is an interactive step and you are issuing a non-interactive authorization request the response would indeed be login required.
For this particular situation this ends up being the solution, but this also applies as a general recommendation; you should avoid using localhost for development purposes. It does not provide you with any noticeable benefits and only means that your development experience is deviating from the production environment.