Before you require SSO, after you complete the rest of the connection configuration, log out and then use SSO to log in.
If you require SSO before you use SSO to log in at least once, then you will not be able to log in.
By default, users can either:
Use SSO.
Use their email address to create an account directly.
You can require users to only use SSO.
After you complete the connection configuration and then log in with SSO, to require your users to only use SSO, check the Require SSO for login checkbox.
Selecting the provider and configuring the connection
Click the SSO provider to use, then configure the connection to the SSO provider.