Run live checks against the auth stack. Use this when Google sign-in or email login fails.
redirect_uri_mismatch — The redirect URI is not registered in the OAuth provider.access_denied — User canceled the consent screen.invalid_client — OAuth client ID/secret misconfigured.invalid_grant — Expired or reused authorization code.unauthorized_client — Client not allowed to use this flow.server_error / temporarily_unavailable — Provider-side issue; retry.