Hi @TheRobBrennan!
We have submitted a PR to your repository with a solution to your problem. Although the code there works, be aware that that is not the best approach. It would be way better if you had a Callback route/component to handle the authentication process when Auth0 redirect users back to your app.
For example, in this article The Complete Guide to React User Authentication with Auth0, you can see that in action. Just search for the “Securing your React App” section on it. I hope it helps!
Thanks! 