As the Win7 can be comosed in Horizon view 6.2.3 but Win10 can not, it always shows
View Composer agent initialization state error (6): Unknown failure (waited 0 seconds)
Resolution:
Delete this Subkey:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\BFE\Security
Restart the virtual machine.
Ensure Services are running. This image can be used for snapshotting.