Hi @chrisb,
Thanks for contacting the Auth0 Community!
I understand that you are encountering issues enabling Sign Up for your Universal Login.
First, could you please go to your Auth0 Dashboard > Applications > YOUR_APP > Connections and check which Database Connections are enabled for that application?
Depending on which Database Connection you have enabled, navigate to each connection and switch off the Disable Signups toggle.
Once that is complete, your application will allow users to sign up.
Please let me know if this resolves your issue.
Thank you.