My organisation has quite a number of computers running Windows 8.1 SL (OEM) as it came installed when purchasing the machine. We have recently purchased a Volume License (MAK) Key in order to upgrade these computers to Window 8.1 Pro.
I click on "Get more features with a new edition of Windows" and enter the new MAK key and get the following message: "This Key won't work. Check again or try a different key"
I have found a way to get our Windows 10 SL machines to work but that method does not work with Windows 8.1
We also have Windows 7 computers that I will need to do the same with.
How can I get this to work as I do not want to have to reinstall all these computers?