Launch the Terminal from Applications > Utilities to fix Mac Outlook 2019 search not working issue.
Now, press Enter after typing each command as listed below,
% sudo mdutil -i off /
% sudo rm -rf /.Spotlight* sudo rm -rf /.metadata_never_index
Restart the system and also type the below commands in the terminal
% sudo mdutil -i on /
% sudo mdutil -E
Then, wait until the Spotlight reindexes the entire drive. Once the indexing is completed, try to use the MS Outlook search.