Admin LDAP Servers - <LDAPSERVER> - Server Settings

LDAP E-mail Attibute : mail
LDAP User First Name Attribute : givenName
LDAP User Last Name Attribute : sn
LDAP User Identification Attribute : uid
LDAP Group Membership Attribute : groupMembership

LDAP Group Object Class : Groupofnames
LDAP User Object Class : inetOrgPerson

"Test Now" shows everything successful with the following included in the onscreen report

Opening the connection to the LDAP server ... Successful.
Authenticating the account ... Successful.
Testing the search function ... Successful.
Found users. Verfying attributes ...
mail : Verified.
uid : Verified.
Found groups. Verfying attributes ...
groupMembership : No value could be found.

Periodic Update Settings - update now - returns "Periodic Update failed"

Can anyone tell me what the correct attibute fields should be?