Adding users as contributors in change management

Hi everyone,

I am facing some issues in adding some users as contributors in change management.

The users have almost all the required privileges like

1. REPO.MODIFY_FOREIGN_CONTRIBUTION.
2. REPO.MODIFY_OWN_CONTRIBUTION.
3. REPO.MODIFY_CHANGE

When I click NEW CONTRIBUTOR , I am unable to see the User in the list.

Is there any other special privileges that are required. I have gone through the developer guide also to resolve the issue but couldn't find any missing privileges.