A number of Windows 10 Pro users have received warnings to downgrade to Windows 10 Home due to possible problems with Microsoft’s activation servers.

Reports came in overnight that Windows 10 Pro systems were displaying a notification that the user’s license key was invalid for the Pro edition and advising to install Windows 10 Home instead. The message also gives users the option of purchasing a new key to reactivate their copy of Windows 10 Pro, despite users having a genuine Pro key.

The problem initially appeared to be affecting users who took advantage of the free upgrade to Windows 10 and who were previously running Windows 7 Ultimate or Windows 8.1 Pro. However, reports emerged later of similar problems on PCs that had only ever run Windows 10.

SEE: Windows 10 power tips: Secret shortcuts to your favorite settings (Tech Pro Research)

One of those affected reported that a Microsoft support agent said the firm was aware of the problem affecting users in Japan, Korea, America and other countries.

The agent said some Windows users might be receiving messages saying Windows is not activated and that this was due to “a temporary issue with Microsoft’s activation server”, which would be fixed in “one to two business days”.

Other affected users report being told to wait a few hours for the problem to resolve itself. Microsoft had not responded to a request for comment at the time of publication and the @MicrosoftHelps Twitter account isn’t clear about whether there is a problem with the activation servers.

The reports of Windows activation problems follow Microsoft’s decision to halt the rollout of the Windows 10 October 2018 Update to resolve a data-wiping bug.

Since then, multiple reports of bugs in the Windows 10 October Update have emerged, including an issue handling .ZIP folders and a bug that caused Task Manager to report the incorrect CPU utilization.

A subsequent fix for the 1809 build resulted in some HP systems suffering from the Blue Screen of Death, which triggered another update to fix issues with driver compatibility.

In the wake of the October Update rollout being halted, Microsoft has faced calls to slow the pace at which major feature updates are applied to Windows 10 to ensure new releases are more stable. For its part, Microsoft has introduced a way for those testing early builds of the OS under the Windows Insider Program to flag the severity of bugs.

UPDATE: Microsoft later confirmed there was a problem with activations for a “limited number of affected Windows 10 Pro customers” and as of Friday this issue appears to have been resolved for most users.

Read more about the Windows 10