We have an individual user who has access to multiple SharePoint Online sites within the organisation as an Owner. For most of the sites, that user is able to use the top Search bar in order to find results (including documents, etc).
However, when they are on using one particular Group Enabled site, the search bar returns absolutely no results for any query, even though they are an Owner on that site. If they click on "Show more results", SharePoint comes up with no results. The user is able to find the required documents by manually navigating to the associated Document Library, so they clearly have the required permissions.
Before I submit this to Microsoft for further troubleshooting, I wanted to see if there was anything obvious I was missing. Thanks in advance!