Users of perpetual Microsoft Office 2016 and 2019 licences report that their installations suddenly lost activation, apparently requiring repeated product-key entry, restarts and account sign-ins. The issue matters because affected devices can enter reduced-functionality mode, creating major disruption, particularly for organisations managing large numbers of installations.

Many users suspect the problem is linked to optional Windows update KB5002907, which helps outdated Microsoft 365 Apps resume updating, although Microsoft has not confirmed that it caused the activation failures. Office 2016 and 2019 support ended on 14 October 2025, but Microsoft had said the software would remain usable; reactivation problems therefore conflict with users’ expectations.