While it seems that many Windows 8.1 users availed themselves of the free upgrade offer for Windows 10 and are now on Microsoft's latest OS, there are still some who still use the previous installment. For those users, Microsoft usually pushes out monthly updates that contain a number of patches and this month's update seems to have caused a bit of a hitch in Microsoft's plans.
According to user reports, the September monthly rollup, tracked under KB4038792, is preventing users from logging into their PC with a Microsoft account. Microsoft has confirmed the bug is caused by the September update and promised it's working on a fix. However, in the meantime, the only recourse for users affected by the problem, as stated by support personnel on a Microsoft forum, is to log in using local accounts and wait for the fix to be released, for which there is no ETA yet.
The statements by Microsoft staff on the forum read:
This is a known bug in Windows 8.1 after the latest September update. Our Support Engineers are already looking into it and doing their best to resolve it as quickly as possible so as to minimize the inconvenience to our customers.
As of the moment, affected Windows 8.1 users may use a local account instead of a Microsoft account while our engineers are fixing the bug. We have not yet received any news about when the fix will be released. We'll update this thread once it's available.
While the company is working on a fix, users may use local accounts for the time being, despite the lack of syncing for certain features. Alternatively, despite the free upgrade offer for Windows 10 being officially over, Microsoft is still allowing users to upgrade by either using an Assistive Technologies loophole or by using a valid Windows 7 or Windows 8 key to install Windows 10. As Microsoft edges towards putting Windows 8 out to pasture, it might be high time for those users to upgrade to the company's latest platform.