Joomla account creation fields not appearing on profile forms
Community builder has a plugin called Community Builder System plugin that can be set to redirect or rewrite Joomla user component URLs. Perhaps this interferes and as a result keeps the field set of user registration URLs inaccessible and so out of view in the profile form.

I thank you for your check-list of steps to get the account creation fields to show themselves. It rescued me when I did not know how and why they kept not appearing in a new profile I was trying to get working.
So: well formulated question that answered me in my quest.