Upgrading your operating system to macOS 10.14 or later will allow Office updates to be delivered for your apps. If you continue with an older version of macOS, your Office apps will still work, but you'll no longer receive any updates including security updates. As of the December 2020 (build 16.44) update for Microsoft 365 for Mac or Office 2019 for Mac, macOS 10.14 Mojave or later is required to receive updates to Word, Excel, PowerPoint, Outlook and OneNote.
