If unsuccessful, call Microsoft 80 or 88. Hopefully it will get you to the point where you can re-install it on your computer. Unfortunately I don’t recall the steps you need to follow through but If you can get through the process chances are Microsoft’s assigned product key will be different than your purchased product key. Even if you hadn’t used a Microsoft account and/or didn’t purchase it through the store, try anyway. If you have a Microsoft account, try this. In 2017 he had to re-install it and the following recommendation worked for him.
I had used my Microsoft account to purchase it through the store. I installed Microsoft Office Home & Business 2013 in 2015 on a laptop I gave my son.
