Hi Abhishek, This is purely due to lack of Identity source. You need to add an Identity source to the Vcenter.
Login to Vsphere web client with administrator@vsphere.local
go to Home
go to Administration
then go to Configuration Tab
Then click on Identity source
Click on Add Button(+ sign)
Select the first option (Integrated mode with Windows)
it will pick up your domain name.
Press Ok and wait for a sec. It will start showing up Domain name in the Identity Source List.
Now go to Vcenter and click on Manage.
Select permission Tab and you will be able to see your domain there in the list.
-Thanks@ !