Dear cellyoolar_006,

Thanks for posting in Microsoft Community.

First, my pleasure to assist you.

As per your description, please don’t worry, we can work together to narrow down and resolve the situation.

Generally, if you have purchased Office 2021 with product key, before you begin install and activate Office, you will need to Redeem your product key to associate it with your Microsoft account.  Go to office.com/setup and sign in with your new Microsoft account* and then enter your product key to redeem it. Redeeming your key is what add your Microsoft account to Office, and you only have to do this once. 

If you redeem your Office key to Microsoft account, you may access that account https://office.com/myaccount with your associated Microsoft account to check whether the Office Home and Student 2021license is listed under your subscriptions and click to reinstall or activate with your Microsoft account. For your reference: Download and install or reinstall Microsoft 365 or Office 2021 on a PC or Mac

Your understanding and patience will be highly appreciated. I hope that you are keeping safe and well!

Sincerely,

Waqas Muhammad