Why my fields are not displaying in the registration form when selecting User+Admin Access level?

The access level ‘User + Admin’ is meant to display the field to admins
and the logged-in user (on the website) only. So, once a user is logged
in, she/he would see these fields. If you want to display the field publicly to all unregistered (guest) users, then 
you need to set the field to Public access level.