If search stops working in Office 2019 (specifically Outlook), you can force a refresh by going to

Microsoft Office 2019 comes with a range of new features and improvements that make it an essential upgrade for anyone using previous versions of Office. Some of the key new features include:

Windows Search builds a catalog of terms from your emails, appointments, and contacts so you can search them electronically rather than scanning files one by one. Rebuilding the Index:

In Microsoft Office 2019, "indexing" refers to the background process that catalogs your emails and files to provide near-instant search results. How it Works: