Unable to add AD groups in Permissions using Web vSphere ESXi 6.5

Hi,

   This is a new setup, and installed ESXi 6.5.

   I was also able to add my ESXi 6.5 to the active directory, and I am able to add AD users under "Manage Permissions".  However, I am unable to add AD Groups. 

   The error message is "The user or group named "mydomain\adgroup" does not exist.

   However, I AM ABLE to add those permissions using the vSphere Client from Windows.  Those AD groups works fine.

   But using the vSphere WebClient won't work.

   Any ideas why?

Thx...