cannot use office products

If Microsoft 365 is active but the desktop apps cannot be used, the most common causes are signing in with the wrong account, multiple Office installs, or a preinstalled Office version asking for activation.

Try this in order:

1. Confirm the licensed account
   • Sign in to Services & subscriptions at https://account.microsoft.com/services.
   • Verify that the Microsoft 365 subscription is listed there.
   • If it is not listed, sign in with another Microsoft account that may have been used for the purchase.
2. Sign in inside an Office app with that same account
   • Open Word or another Office app.
   • Go to File > Account.
   • Make sure the signed-in account matches the account that shows the subscription.
   • If needed, sign out and sign back in with the correct account.
   • If available, use Update License under Product Information.
3. Check for multiple Office installations
   • In Windows, open Control Panel > Programs > Programs and Features.
   • Search for office.
   • If more than one version is installed, uninstall the version not being used.
   • Restart the PC.
   • Open an Office app and sign in again.
4. If Office was preinstalled on the device
   • A preinstalled copy can show prompts to try, buy, or activate, and may ask for a product key or similar activation information.
   • If purchased directly from Microsoft, a product key usually is not needed. The subscription is tied to the Microsoft account used for purchase.
   • If the installed apps do not match the product owned, activation can fail.
5. If activation still fails
   • Run the Microsoft 365 sign-in troubleshooter on Windows 10 or later: https://aka.ms/SaRA-OfficeSignIn
   • Or use guided support in the browser: Try guided support

About the “certificate #” prompt: the supported guidance indicates Office activation should normally use the Microsoft account associated with the subscription, not a product key, when purchased directly from Microsoft.

If the subscription appears correctly in Services & subscriptions and Office still asks for activation details, use the account shown there to sign in to the app and update the license.

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