A bug in the Windows 10 Search is causing blank results to be shown in both the Start Menu and in File Explorer search. Microsoft has stated that they have pushed out a fix and that it should be resolved for ‘most’ users. If you already implemented the fix below, you can enable Bing search again (instructions below) and see if the issue is resolved for you. If it is not, you will need to use the fix again and wait for Microsoft to resolve the issue.
Source: https://www.bleepingcomputer.com/news/microsoft/windows-10-search-is-broken-and-shows-blank-results-how-to-fix/