my one time purchase of office home 2024 no longer recognizes my product key

Hello, thank you for reaching out to Microsoft Q&A.

If you’ve already redeemed your product key, you should see your perpetual license (Office Home 2024) listed under your Microsoft account here:

https://account.microsoft.com/services

If you’re suddenly being asked to activate Office apps on your Mac, you can use the Office License Removal Tool to remove all previous Office license information from your Mac. After running the tool, reactivate Office by signing in with the same Microsoft account that is associated with your perpetual license.

You can download the Office License Removal Tool from the official Microsoft website here:

Download and run the license removal tool

Let me know if you still need more help.

For a one-time purchase of Office Home 2024, the product key is only used once to redeem and link the license to a Microsoft account. After that, activation is done by signing in, not by re-entering the key. The message that the key is “already in use” means it has already been redeemed and cannot be used again directly.

Follow these steps:

1. Stop trying to re-enter the key
   The key has already been redeemed and is no longer needed for activation.
2. Sign in with the correct Microsoft account
   • Go to the Services & subscriptions page: https://account.microsoft.com/services
   • Sign in with the Microsoft account that was used when the product key was first redeemed (this may be different from the email used at Best Buy).
   • Confirm that “Office Home 2024” (or the exact product name you purchased) appears under “Products you've purchased” or “Services & subscriptions.”
3. If Office Home 2024 appears in your account
   • On the same page, select Install next to your Office product to download the correct installer.
   • Run the installer and complete setup.
   • Open Word or Excel; when prompted to sign in, use the same Microsoft account from step 2.
   • Office should activate without asking for the product key again.
4. If Office Home 2024 does not appear in any Microsoft account
   • This indicates the key was redeemed under a different account than the one being checked. Try any other Microsoft accounts that might have been used.
5. If Office still shows an activation error or keeps asking for a key
   • Uninstall all existing Office/Microsoft 365 apps from the device.
   • Restart the device.
   • Reinstall Office from the Services & subscriptions page as described above and sign in with the correct account.
6. If the product key has been blocked or is invalid
   • If an error appears stating “This product cannot be activated because the product key is not valid”, the key has been blocked and will no longer work. In that case, contact Best Buy (the seller) and request a refund or replacement, as Microsoft indicates blocked keys are often stolen or fraudulently obtained.

The key point is that access to the apps now depends on signing in with the Microsoft account that holds the redeemed license, not on reusing the product key.

References:

• Where to enter your Office product key
• "Product key is not valid" error when activating Office
• Switch to Office Home and Business 2024
• How can I install Home Office 2024 with my Microsoft Account with your directions. - Microsoft Q&A