Processes in Microsoft 365 for setting up Office apps, redeeming product keys, and activating licenses.
Once you redeem a product key, the license is permanently linked to the Microsoft account you used to redeem it. That account will hold your license, so you no longer need the product key.
Sign in to that Microsoft account here: https://account.microsoft.com/services
Can you find your Microsoft 365 subscription there, and does it show as active?