Using Classic Outlook on Windows for personal email, calendar, and contact management
First of all, there is no "Update and Security" button in settings. There is an "Windows Update" button and there is Privacy and Security. No update and security. So there is no troubleshoot to find, search index and so on. So it would appear none of your suggestions applies to my situation. I have rebooted Outlook and Windows and "repaired" 365 without effect.
Windows tells me I am up to date. I am running Windows 11, version 23H2 and MS 365 Outlook. I get the same message over and over: