To resolve this, follow these steps:
Log in to the vSphere Web client as the admin account (admin@System-Domain) you created during the vCenter server installation
Browse to “Administration -> SSO Users and Groups”
Browse to the “Groups” tab and click on “__Administrators__”
Click “Add Princilpals”
Select our vCenter server as the identity source and add the user “Administrator” to the list
Then login as “Administrator” in to the vSphere Web client, you should see the vCenter server listed in the objects. No further registration needed.