A new week, a new Windows 10 bug. As it seems there is an issue specific towards Windows 10 Pro license holders, for a number of people the license deactivates or downgrades itself rendering the Windows 10 build useless in a couple of days.

There is an ongoing issue about Windows 10 suddenly shown as deactivated. The affected users need not to do anything as it is a known issue. Here is what was told by Microsoft Chat support:

-- Microsoft -- We have 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 

We are aware of reports that some customers’ Windows 10 Pro and Windows 10 Enterprise machines are not recognizing their licenses as activated. Users may receive the following notification: “Error: you are running Windows 10 Pro, but you have valid digital license for Windows 10 Home," or one of the following error codes 0X803F8001, 0xC004C003. We are actively working to resolve this within 24 hours. You can still use your PC; however, the watermark will appear until activation is restored. Thank you for your patience.

We will update this post with additional information as needed and once activations are restored.

Thanks to Vijay_Verma and Daniel for the information. Also new, Users report that Windows activation troubleshooter might say You have a Windows 10 Home license but you are running Windows 10 Pro. You are advised to ignore that message and wait for the fix.