The reason behind the failure in the activation occurs as each install button associated with a unique product key and can install on one pc only. Some cases if the user has multiple copies of office than also it shows activation error. However, if you are using Microsoft office 2016 or other, you need first to uninstall it completely. If you are installing 2019 directly, then it does not need any extra efforts. You need to upgrade your windows if you need the new version of office 365. However, as I said the crack version works on Windows 10 only. I guarantee you will love it after using it. Some new tools are also added for better performance.