Windows 10 upgrade activation failure

I downloaded a windows 10 image from the volume licensing site and used that to upgrade a HP Elitebook from Windows 8.1 which had been activated. The license key is available in the BIOS and can be accessed from the command prompt using:
wmic path softwarelicensingservice get OA3Xoriginalproductkey
Unfortunately, after the upgrade, the license did not automatically activate, in fact, Microsoft could not activate it without using a digital product key. When I downloaded an image using the Media Creation Tool, it worked great and the key automatically activated.
I now have 25 computers upgraded but do not know which ones Microsoft had to assist me with and which were upgraded using the newer image. Is there any way of finding this out?
I am worried that if I have to reinstall after the free upgrade period, the windows key currrently installed will not be recognised and I will have to buy a new license or go back to Windows 8.1