Because I already used the key for office 2019 home & student once I cannot install it again on the same device. I tried for over two hours with the Microsoft assistant but it does not work. I'm also confused, because sometimes the reply from the system is, that I have no abonnement, but office 2019 is no abo. Reinstall Office 2021 from the Microsoft Store Library. Select Start and then open the Microsoft Store app on your Windows device. From the Microsoft Store app, select Library icon > Apps tab (If you can see All tab in Library, select All tab.) Turn off the Show installed products only filter under Sort and filter (If you select All tab, skip 2ELV9.