My Office account was activated by the wrong person's email account

Dear @David Gannon,

Thank you for posting your question in the Microsoft Q&A forum.

Please understand that our forum is a public platform, and we will modify your question to cover your organization domain name in the description. Please notice to hide these personal or organization information next time you post error or some information to protect personal data.

Based on your description, the Office product key has already been redeemed and linked to the former employee’s Microsoft account, so it cannot be reassigned directly on the device. For one-time purchase versions of Office, the license becomes permanently associated with the Microsoft account used during the initial activation. This means re-entering the same key under a different account will not work.

However, if this is urgent, you can try to contact Microsoft Support team and request a license transfer due to employee departure, and provide: Product key, Proof of purchase or Business ownership details.

You can use this link to find the appropriate contact number: Global Customer Service phone numbers - Microsoft Support   

Note: Please understand that as forum moderator, my primary goal is to provide helpful guidance and support through general troubleshooting steps. While I don’t have access to internal systems or test devices required to resolve backend issues, I truly appreciate your understanding of these limitations. I genuinely hope the information I share helps guide you in the right direction, and I'm always here to assist as much as I can within my scope.   

I hope information above helpful. If you have any other questions, please feel free to reach out.

The product key and activation cannot be moved from one Microsoft account to another. If Office was redeemed and activated under the former employee’s Microsoft account, that key is now permanently bound to that account and cannot be reassigned to a different business or personal email.

To use Office on the laptop for the new employee, use one of these supported options:

1. Sign in with the account that owns the license
   • If the business has a Microsoft 365 subscription, sign in to Office on the laptop using a licensed work or school account (for example, a company Microsoft 365 user) instead of the former employee’s personal account.
   • Make sure the correct account actually has an active license by signing in to the Microsoft account services page and confirming that the Office product or Microsoft 365 subscription is listed there. If it is not listed, that email address does not own the license.
2. Assign or reassign a Microsoft 365 license (for business subscriptions)
   • In the Microsoft 365 Admin Center, go to Users → Active users.
   • Select the user who should own and use Office (for example, the new employee’s account).
   • Select Licenses and Apps.
   • Under Licenses, select the appropriate Microsoft 365 or Office license and choose Save changes.
   • If the license is already assigned but not working correctly, uncheck it, Save changes, then check it again and Save changes once more.
   • On the laptop, sign out of Office completely, then sign back in with this licensed work or school account and let Office reactivate.
3. If the key was a one-time retail purchase tied to the wrong personal account
   • Office 2016/2019/2021 and similar one-time purchases are permanently attached to the Microsoft account used when the key was redeemed. They cannot be moved to a different Microsoft account or “taken back” from the original account.
   • In this case, the only supported path is to purchase a new license under the correct account or use a Microsoft 365 subscription assigned to the correct user.
4. General activation checks on the laptop
   • Make sure only one copy of Office is installed. Multiple copies can cause activation conflicts.
   • Confirm that the subscription or license being used is active and not expired.
   • Sign out of Office apps on the laptop, then sign in using the correct licensed account (work/school or personal, depending on how Office was purchased).

Do not share or reuse volume or organization-only keys (such as MAK keys) outside the organization that purchased them. If the key came from a third-party reseller and behaves like a volume license (for example, “activated up to the limit of your Multiple Activation Key”), it may not be a valid consumer license and may stop working.

References:

• "This product key has already been used" error in Office
• Unlicensed Product and activation errors in Office
• Microsoft 365 apps activation error "Another account from your organization is already signed in on this computer"
• Microsoft 365 Apps activation error: "That Microsoft account doesn't exist. Enter a different account or get a new one."
• Can't activate Office - Microsoft Q&A
• Theft/Fraud Associated with my Office Product Key. - Microsoft Q&A