Unable to clone a database

Summary:

I'm working with an autonomous database (Apex type) in the Free Tier. I only have one database and I'm trying to clone to a new DB for testing.  On the clone page, the "Create Autonomous Database Clone" is gray, not blue. And if I push it, nothing happens. I've left all the default settings except for the admin password/confirm password.

I've tried cloning from a backup and cloning from the existing DB but I can't get either to work. I don't see any error messages or notifications, the button just doesn't do anything. Any ideas what I can check?