My WMC key was activated online when I first got it and it instantly activated with new ISO I made. I have tried it 2 times now and all is good. Have made any hardware changes to your PC and are trying it on the same PC you first activated it on ? The method I used will only work on the original PC I First activated my WMC key on.
Which ISOs do I need to do this? Are these the needed ISOs ... Core/Pro x86 Core/Pro x64 Enterprise x86 Enterprise x64
You need to un-mount before you can delete try this Dism /unmount-wim /mountdir:C:\win81\mount /commit