5a693e87_Plus__known_issues____RealVNC___Workaround
[ID] 402 [Description] Connecting users might not be authenticated automatically in a Kerberos network environment if members of an Active Directory group. [Status] Fixed in 1.2.6. [Workaround] 
Create an Intel AMT user for each AD user; do not create an Intel AMT user that is an AD group.
VNC® Viewer Plus (known issues) - RealVNC®
Workaround