Microsoft is investigating a known issue triggering “Product Deactivated” errors for customers using Microsoft 365 Office apps.

According to online user reports on Reddit and Microsoft’s own community website, affected users randomly received these “Product Deactivated” errors in Office apps, prompting confusion and disruptions.

As Redmond explained in a support document published on Thursday, these problems stem from licensing changes initiated by administrators.

More precisely, the known issue arises when moving users between licensing groups (including Azure Active Directory groups or synced on-premises security groups) or switching user subscriptions, such as changing from an Office 365 E3 license to a Microsoft 365 E3 license.

It can also be triggered when admins remove and re-add users to license groups, adjust license or service plan settings, or toggle the “Latest version of Desktop Apps” service plan under the Microsoft 365 subscription.

To address this deactivation issue, customers can click the “Reactivate” button on the error banner and sign in when prompted. Alternatively, they can sign out of all Microsoft 365 apps, close them, and restart them before signing back in.

If the issue persists, users are advised to contact their administrators to check if the Microsoft 365 subscription has expired. Admins can check subscription details under the Microsoft 365 subscription management portal.

For further troubleshooting, Microsoft advises users with open support cases to provide diagnostic data to its engineers, collected using the Office Licensing Diagnostic Tool, which can help find the root cause of licensing-related issues.

Affected users are also prompted to provide support engineers with the logs stored in the %temp%/diagnostics directory.

While Microsoft has yet to share a timeline for a fix, its engineering team is actively investigating this known issue. The company encourages affected users and administrators to monitor its support channels for updates.

Last month, Microsoft also shared a temporary fix for a known issue affecting Microsoft 365 customers that causes classic Outlook to hang or freeze when copying text.

In September, the company fixed another bug that crashed Microsoft 365 apps (i.e., Outlook, Word, Excel, OneNote) when typing or spell-checking a text.