LDAP Configuration done through MWS not working!!

Hi Gurus,
This is the first time I am trying to set up IS to used LDAP authentication that is done by using MWS.
I am using prescribed procedure to set up LDAP via MWS and that seems to have been done ok ; but when I log in to IS and try to set ACLS for LDAP users, it does not show up any users/groups/Roles for LDAP.

What could be possible going wrong?
PS: I reseting the Central User JDBC Alias to none as prescribed ; and not setting up LDAP URL directly on IS side but relying on MWS set up

Thanks for any tips/help offered.