Hi @Phil-Wheeler,
The code described in the article should be working fine without any extra code or settings. Do you get the same error even if you use the full code from the GitHub repository?
Ensure you have chosen the Regular Web Application type when you created your application in the Auth0 dashboard.
Also, if you can give other info about your environment (operating system, firewall presence, or similar) maybe I can try to figure out what is happening.
Let me know