Users report that a recent optional update for out-of-date Microsoft 365 applications might be connected to suddenly deactivated Office 2016 and 2019 installations.
The activation bug cropped up this week and appears to mostly impact Home and Business perpetual license installations, stripping away their authenticated status and forcing users into a loop where they are asked over and over again to re-enter their product key or face deactivation or reduced-functionality mode.
The symptom is that a previously activated copy of Office 2016 and 2019 appears to abruptly lose its activation information, triggering alarming pop-ups and dire warnings that functionality loss is imminent. Affected users say one fix is to re-enter the original product key to restore the activation state.
This would be a fine solution, if the user is sufficiently organized and have that number or numbers to hand. It is not so fine if you're faced with dozens, hundreds, or even more devices affected.
A reader told us the issue "took out our Office 2016 installations."
They added: "First indication is a message in the app you are using telling you that normal functionality has been removed. Also Yellow banners saying you have five days left before you can no longer use the apps.
"It takes multiple product reactivations, restarts and sign in/sign out of your Office account to get it stable."
A glance online shows many users believe the problem is connected to KB5002907. The optional update is for Windows PCs with Microsoft 365 Apps that are more than 90 days out of date. According to Microsoft, "Installing the update can help the apps resume updating and move to a current build for the device’s assigned update channel."
Crucially, Microsoft also said the update is not automatic. However, users affected by the sudden reactivation requirement noted that the issue began around the same time the update appeared.
Support ended for Office 2016 and 2019 on October 14, 2025. As such, Microsoft is under no obligation to release updates for the software. That, however, hasn't stopped it from occasionally releasing a patch that breaks stuff, for example the Paste problems that surfaced after an Excel patch. Unexpected consequences from an Microsoft 365 update are not unusual.
Microsoft also has form when it comes to bricking old versions of software, although in the case of the Apple version of Office 2019, that bricking was deliberate due to the expiration of a certificate that dropped the applications into "reduced functionality mode" – opening and printing still worked, but creating, editing or saving? Perhaps sir or madam might consider a subscription to Microsoft 365?
As a reminder, when Office 2016 and 2019 for Windows reached the end of support, Microsoft assured users they could continue using the products regardless. It did not mention the unexpected need to enter a product activation code… ®