I have just updated an existing site to on a staging domain on the same server.
Old version: WP: 5.7 CIVI 5.29
New version: WP: 5.8 CIVI 5.39
On the old site a user can register via a profile in a page using a shortcode.
In the new version the registration form exists BUT there is no Username / Password fields.
The profile settings has "Account creation required" checked.
Anyone can register in WP settings is checked.
I have deactivated other plugins and changed the theme - but this doesn't affect the issue.
I am loading the staging site in a clean browser - so I am NOT logged in.