Processes in Microsoft 365 for setting up Office apps, redeeming product keys, and activating licenses.
Hello !
What exactly do you see on your screen when you launch Office ? You should see an option to sign in to activate Office : that’s the option you need to select.
Using a product key won’t be necessary, especially if you have a Microsoft 365 subscription and have already activated your license.
Have a look at this Microsoft support article : https://support.microsoft.com/en-us/office/activate-office-for-windows-5bd38f38-db92-448b-a982-ad170b1e187e
Looking forward to your answer !