If you are using macOS 10.13 or earlier and Microsoft 365 for Mac, your Office apps (Word, Excel, PowerPoint, Outlook and OneNote) will no longer be able to receive any updates including security updates after November 10, 2020. Upgrading the operating system to macOS 10.14 or later will allow app updates to proceed.
Please visit the following webpage of Microsoft’s announcement on the subject for details:
User Services Team
Tel: 3917 6220