Using older versions of Outlook for Mac for personal email and calendar
If you need Legacy Outlook for Gmail or other accounts unfriendly to new version:
As another friend said: re-index the whole drive. It's simple and works. Just drag Macintosh HD to the Spotlight exclusion privacy tab. Quit SysPref. Restart. Remove from exclusion. Restart computer.
I can't believe this is a 'thing.' The problem is Outlook seemingly needs a clean handshake to the overall Spotlight index or it doesn't make the leap. So silly, as it a simple algorithm to look for sort/hierarchy discrepancies...have the Spotlight/Outlook search algorithms for mail entries match. Either Apple/MSFT isn't allowing this to occur by default based on versions of OS or Outlook.
Good news? Problem solved...for now. Until a new update breaks it again, Then re-run the steps above.