If you clicked your app on your IdP, and you see an error similar to the one below, it means your login custom route listed in your SPA’s Allowed Callback URLs. The login custom route is the one you provided in the redirect_uri query parameter value in the IdP-initiated SSO setting’s Query String. Without route in the list, auth0 won’t be able to call it.
Callback URL mismatch.
The provided redirect_uri is not in the list of allowed callback URLs.
Please go to the Application Settings page and make sure you are sending a valid callback url from your application.
invalid_request: IdP-Initiated login is not enabled for connection "connection-name-here".
unauthorized_client: Callback URL mismatch. "yourdomain.com/customloginroute" is not in the list of allowed callback URLs