Openfire 3.9.3 openldap 2.4, users not listed, groups not listed

after installing openfire ldap user and group backend.

admin is in ldap and password is read from ldap (can change it there)

at user summary, the total number of users configured in ldap is listed correct, only the table is empty.

at group summary, the total number of groups configured in ldap is listed correct, only the table is empty.

what are the minimal object classes for users?

what are the minimal object classes for groups?

do i need to do some field mapping and how to display users and groups? Or am i missing object classes that hold fields to be displayed?