After upgrading the vSphere infrastructure and VMware Tools to version 6.5, the “Upgrade VM Compatibility”
option is grayed out in the vSphere Web Client. (See Exhibit.)
What must the administrator do to enable the VM compatibility upgrade?
VMware Tools should be upgraded last.
Restart the ESXi server.
Uninstall VMware Tools.
Power off the virtual machine.
If Upgrade VM compatibility is grayed out, it is because VMware tools are not installed or they are running the
current version. For that you have to restart ESXi server. This way VMware tools will be upgraded or it will ask
you to install it.