Internet access is required to install and activate all the latest releases of Office suites and all Office 365 subscription plans. For Office 365 plans, Internet access is also needed to manage your subscription account, for example to install Office on other PCs or to change billing options. Internet access is also required to access documents stored on OneDrive, unless you install the OneDrive desktop app. You should also connect to the Internet regularly to keep your version of Office up to date and benefit from automatic upgrades. If you do not connect to the Internet at least every 39 days, your applications will go into reduced functionality mode, which means that you can view or print your documents, but cannot edit the documents or create new ones. To reactivate your Office applications, simply reconnect to the Internet.
You do not need to be connected to the Internet to use the Office applications, such as Word, Excel, and PowerPoint, because the applications are fully installed on your computer.