It must be getting the client_id out of the session, which would no longer exist after a successful login.
As for this particular error, we have a feature in beta right now that a few customers are trialing that allows you to configure either a tenant level or client level URL where you can redirect a user to if they login using the back button or a bookmark (basically any scenario where the login session is no longer valid). Watch the product announcements for it to arrive soon!
Please NOTE, the URL should be a login URL that will redirect the user back to /authorize at Auth0. If they had previously logged in, they will be directed to your callback automatically with the appropriate state.