If you have purchased a subscription to Office 365, you can find your product key in several ways:
The key follows a specific five-by-five format: XXXXX-XXXXX-XXXXX-XXXXX-XXXXX . It acts as a "redemption key" rather than a permanent license. Once entered, the key is permanently linked to your . After this initial setup, you no longer need the physical key; you simply sign in with your email and password to activate Office on any compatible device. Where to Find Your Product Key product key for microsoft office 365
If your product key doesn't work, try the following: If you have purchased a subscription to Office