You can resolve the Outlook search not working issue by following these instructions. Firstly, try rebuilding the Outlook index as it can fix the issue. The use of an older Outlook version can be the reason why your Outlook search is not working. So, look for any updates from your Microsoft Office. You can also try to fix the issue using the registry. To use the Registry method, open the Run dialog by pressing Windows key + R. Next, enter Regedit and tap Enter. Once the Registry Editor opens, click Ctrl + F, and in the search menu, type HKEY_LOCAL_MACHINE SOFTWARE Policies Microsoft Windows Windows Search. Now, right-click and select New Dword( 32-bit). Name the new DwordPreventIndexingOutlook and give the value 0. Once done, press OK and restart your system.
Please read the originial post here: https://prompthelp.us/blog/outlook-search-not-working-in-windows-10/