Processes in Microsoft 365 for setting up Office apps, redeeming product keys, and activating licenses.
An Office product key can only be used once to link the Office licence to your Microsoft account, after that the licence should have become associated to your Microsoft Account as a digital licence online and it is from there that you can re-install Office without the need for a product key:
https://account.microsoft.com/services/
Do you find your Office licence listed there.