Hi,
It is because instant clones use VMFork technology.
This technology is only available since vSphere 6 Update 1.
In addition they need virtual hardware version 11 to work.
excerpt from Horizon Documentation:
Instant clones have the following compatibility requirements:
- vSphere 6.0 Update 1 or later.
- Virtual machine hardware version 11 or later.
Also note that for best performance/compatibility, vCenter and ESXi should be the same version.
Kind regards,
Michael
