Microsoft 365 features that help users manage their subscriptions, account settings, and billing information.
If your Office is the standalone version of Office Home and Student 2019, then the error you are seeing is caused by an update on the 13th of July, many people are seeing the exact same error, after that update, it is no longer possible to upgrade the security certificates on that version of Office on a Mac, your Office apps will go into Read Only mode, on the link below they provide full details on that update.