Yesterday I fell foul of this bug:
 
https://news.softpedia.com/news/how-to-fix-the-windows-10-activation-bug-523696.shtml
 
Windows suddenly said it was not activated, and I actually had a Windows 10 Home license with Windows 10 Pro installed.
 
All I had done, was add a "K" drive mapping, so that my Kontakt library path could be the same between my desktop and laptop. However, it looks like Windows interpreted this as a major hardware change and deactivated my system... then the bug stopped me from re-activating, with the nonsense message about Windows 10 Home.
 
Luckily my previous backup was on Nov 4th, so I re-imaged my drive and got it working again.
 
The post above doesn't mention major hardware changes as being the cause of this bug, so I guess it's possible that this could happen for other reasons. It does say that it is happening to a lot of people though. I was waiting on the phone to Microsoft for around 20 mins, before eventually deciding to give up and re-image my drive.
 
So, if you've got a way of backing up an image of your drives - now's the time to do it!
 

That's interesting...Know what my first thought was? Microsoft did this "by design" so they could root out the pirated $9.99 thru $49.99 copies of windows 10 that have been sold around the world. 
I know that's not it, but slick idea.
 
I do have recent images also....But I also have a legal $199.00 version of Win 10 Pro direct from Microsoft...
 
Thanks for posting that article..................

There is a post on the tenforums.com about a Microsoft problem with some activations.
See if this applies to you.
https://www.tenforums.com...kenly-deactivated.html

Recently bumped into this...
Just reentered the product key... and Win10 Pro activated just fine.

Jim Roseberry
Recently bumped into this...
Just reentered the product key... and Win10 Pro activated just fine.

Unfortunately mine was an upgrade from Win 7 Pro, so it's using a digital license rather than a product key.
 
I'm just glad I had a recent image of my hard disk I could restore.

+1
Backup Image File is important... (protection against many different issues)

Jim Roseberry
Recently bumped into this...
Just reentered the product key... and Win10 Pro activated just fine.

This is what is confusing about W10.  Those of us from the free upgrades have a product ID. Is this the same?

Windows 10 Product ID and Product Key
 
https://answers.microsoft...4e40-a7d7-d8402ad194ea
 
The above thread applies if you upgraded from a previous version of Windows, or bought a new system with Windows pre-installed.
 
If you buy a new copy of Windows, you should receive a product key to activate it with.

FWIW, The copy I had to "reactivate" a few days back was an upgrade to Win10 from Win8.1.
It was a clean install... but the install key from Win8.1 *is* the install key for Win10.
In this particular case, there was no change in hardware, the "Windows is not activated" notification just popped-up.
I re-entered the product key and Win10 activated without issue.