Could you please tell us what error do you get when you login to vcenter?
If you add the user(say user1)to the __Administrators__ group in SSO admin and try to login to vcenter using smae user(user1), login should be sussccesful but you can not manage or view the VC.In case if you want to manage VC with the same user then, you have to give VC permession to the same user.