Have the same issue with one of my customer. Some sites have no results. When I'm in the site and enter * in the search bar, no results. All setting are ok. (Permissions ok, Versions are major, display search results at site and library level are ok, site and library reindexed)..
hi Martin, After troubleshooting we found that all site libraries and lists was broken permission and there were no SharePoint groups added. Issue got resolved when we made all lists and libraries inheriting from parent permission