Hi Prasad, you mention CSS which leads me to think that you are still on DCRUM version 12.4 or below. 12.4 is unsupported as of last summer. I strongly suggest to upgrade to NAM 2017 or even 2018.
What version RUM Console are you on? As of NAM 2017 it takes over the CSS function, and CSS is phased out.
LDAP groups should be visable in CSS under User Groups.