On 8 November Many Windows 10 Pro users began receiving messages informing them that they would need to install Windows 10 Home or purchase a "genuine" copy of Windows.
The alert displayed both Windows Insider testers and those who used the latest version of Windows 10 October 2018 update.
Meanwhile, Microsoft has said nothing of substance except that the problem will be repaired at some point. As it turns out, this moment has come.
Jeff Jones is a Microsoft representative Reported:
A limited number of clients encountered an activation issue. Our technicians have repaired it. Affected customers will see the result within the next 24 hours as the fix is automatically applied. After this time, they can continue using Windows 10 Pro as usual.
The watermark will disappear once the repair is applied.