This is happening in our SharePoint Online environment. We have a sub-site that is not returning results for "Search This Site" (osssearchresults.aspx) but when you click on Everything (Enterprise search), results from the site are shown. This shows that the content is crawled since results are returned in Enterprise search. It seems like just the "This Site" scope or site specific search is broken.
Other sub-sites in the Site Collection are returning "This Site" results appropriately so it is not a SC level issue. All settings match the working sub-sites as well.
While setting this sub-site search to use the Enterprise Search Center is working, the preferred method is sub-site search returns "This Site" results first and then the user can go to Everything if they wish.
Any thoughts on where else to look would be appreciated.
Thank you in advance.