Hi @Willy D
We apologize for the inconvenience caused by the Office activation issue.
Based on your description, it appears that your Office Professional Plus 2021 is not a volume licensed version. Could you please confirm whether you purchased your Office from Microsoft or a third-party channel?
- If you bought it from Microsoft, please sign in to your MS Account at https://office.com/myaccount, then go to "Devices", remove this computer.
- After that, navigate to "Subscriptions", re-install your Office for a check.
- Microsoft Office licenses are often tied to the specific hardware of your computer, including the motherboard. If the steps above do not work, it is recommended that you contact Microsoft support to see if they can update the activation information in the background and help you activate Office.
However, if you purchased Office from a source other than the official Microsoft website, please reach out to the seller for instructions on activating Office after changing the motherboard, as their steps may differ from those on the Microsoft website. Thank you for your understanding.
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