Activation/Upgrade Error 0x803fa067

I tried to Updgrade my windows 10 Home to Windows 10 Pro. I tried it with the default key that upgrades Windows 10 to pro without activating it(which is done in the second step).

The Universal-Key for Windows 10 Pro which is published by Microsoft is VK7JG-NPHTM-C97JM-9MPGT-3V66T. I tried that one but I get the error 0x803fa067.

I first tried it with the Windows 10 Settings using the Change Product Key Button in the Activation "Tab" And second with the command slmgr.vbs -ipk VK7JG-... Both methods werent succesfull.

What the error originally means is: you don't have a digital licence or a valid Product Key. I guess either the newly bought laptop was delivered with a fraudulent license( then microsoft is bluntly lying to me)

or the error message isn't quite correct. In this case I would go with my second guess

I am not sure why this Problem occures, so my question is: why do I get the Error 0x803fa067? I am aware of the fact that I could reinstall Windows 10 Pro(which is the way I will probably do it) but I am intrigued to know how I could resolve the Problem without spending those extra 15 minutes.