Hi Dhiman,
What is the scenario you have configured - Centralized / Distributed ?
Can you also please confirm what is the grouping rule you have defined ? i.e MX_PRIV_GROUPING_RULE attribute on GRC repository definition.
Are the privileges you are trying to assign are from same repository or they belong to different repositories ?
If you are assigning a set of privileges belonging to different repositoris, I want you to check the Grouping across the repository definitions section of SAP IDM - Access control configuration guide
I strongly believe this is where you have to check. if possible, please share a screen shot of your GRC repository definition.
Still not able to resolve, let us know :).
All the best !!
~ Krishna