How to Signup from a different domain/reactapp into an already existing and using auth0 react app

I have a react app using Auth0 through the auth0 provider for authentication. I’m building a new react app on another domain that will contain a form for signup, it will be used for redirecting from ads. This form has email and password and also an option to proceed with google too. I want to signup the users redirect them to the current react app and login them.

I tried using auth0-js in the new react app and call authorize with redirectUri to the old app, but I can’t log in the user there, when I try to handleRedirectCallback I get invalid state error missing_transaction, I believe it seems to be because the information is being store in different domains between the applications. Any ideas?