Re: I feel left out....
Windows 7 and greater knows when it is running in a VM.
The GWX software must detect that VM and not allow the upgrade.
It is possible to 'get around' this ........ :)
Google 'SLIC' and think outside the box. :)
As a 1st option go to --> https://www.microsoft.com/en-gb/windows/windows-10-upgrade?ocid=win10_wol_banner_upgrade
Click the download now button.
It will download 'GetWindows10-Web_Default_Attr.exe'
This should perform the 'Upgrade' to Win 10.
I do not know if this will also not work in a VM, try it and see!!!