To their credit, Microsoft were quick to take notice of this obvious bug and one of their support team members went on to say that “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.” This was followed up by a statement from Jeff Jones, a senior director at the company, who went on to say “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.”
If you happen to have this issue, try out the activation troubleshooter to see if the update was applied, and that should help resolve the bug.