Microsoft 365 features that help users manage their subscriptions, account settings, and billing information.
Hello Carl B,
Welcome to Microsoft Community.
I am a Microsoft user just like you, I hope you are doing well.
You did not specify which Office 2021 license you have. However, I will need you to make sure that your copy of Office is activated correctly in any application (Word, Excel, PowerPoint, Outlook).
Open any Office app and click 'File' -> Account section. You will see what Office you have installed, if it is your Office 2021 license.
Please attach a screenshot as this will be helpful.
If it is, I will suggest you delete Office credentials from your PC and try activating again.
To delete Office credentials:
Click Start > Control Panel > User Accounts > Credential Manager> In the Windows Credentials and Generic Credentials section, remove all stored credentials referencing the Office 365 or Microsoft Office: Select the Credential. Click Remove.
Note: Under Generic Credentials, look for any entries containing “OneDrive Cached Credentials” and MicrosoftOffice16 and MicrosoftOffice15 credentials and Remove all.
Please let me know if you need any more assistance.
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Warm Regards