Microsoft

A bug in what appears to be the Microsoft Windows activation service is causing Windows 10 Pro licenses to be downgraded to Windows 10 Home and then stating that Windows is not activated.

This bug appears to be widespread with many users reporting that Windows is stating that their license is not activated and prompting the user to troubleshoot the problems.

Windows 10 Pro not activated
Windows 10 Pro not activated
We can't activate Windows on this device because you don't have a valid digital license of product key. If you think you do have a valid license or key, select Troubleshoot below. Error code: 0xC004C003
If you're having problems with activation, select Troubleshoot to try to fix the problem.

When users perform the Troubleshoot option, Windows is stating that "We found a Windows 10 Home digital license for this device running Windows 10 Pro."

Troubleshooting Completed
Troubleshooting Completed

According to posts about this bug on Reddit and the Microsoft forums, someone had contacted Microsoft via their support chat and was told that Microsoft is aware and are working on the bug. 

"Microsoft has just released an Emerging issue announcement about current activation issue related to Pro edition recently. This happens in Japan, Korea, American and many other countries.I am very sorry to inform you that there is a temporary issue with Microsoft's activation server at the moment and some customers might experience this issue where Windows is displayed as not activated. 
Our engineers are working tirelessly to resolve this issue and it is expected to be corrected within one to two business days "

I personally have contacted the Microsoft support chat and they had no idea what was going on. 

Jeff Jones, Sr. Director, Microsoft., told BleepingComputer in a statement:

“We’re working to restore product activations for the limited number of affected Windows 10 Pro customers.”

Update 11/8/18 5:52 PM EST: According to numerous reports, including a comment to this article, running the Troubleshooter will now resolve the issue. Please give that a try and let us know how it works out.

Update 11/8/18 8:21 PM EST: Updated statement from Jeff Jones, Sr. Director, Microsoft:

“A limited number of customers experienced an activation issue that our engineers have now addressed. Affected customers will see resolution over the next 24 hours as the solution is applied automatically. In the meantime, they can continue to use Windows 10 Pro as usual.” – Jeff Jones, Sr. Director, Microsoft. 

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