Problem:
We had this conundrum, the search results were showing as blank when searching in Microsoft SharePoint 2013 but this was only for files and items, not for people that returned results fine.
After checking the crawler and finding no errors and able to search within the index and finding items I came to the conclusion it was caused by the search center itself not looking where it should do.
Note: there are many causes of this issue, in our case everything to do with the search, permissions and index were fine we just weren’t seeing the results!
Solution:
Browse to your Enterprise search site, normally something like http://intranet.domain.com/search
Click on “site settings” on the enterprise search center site.
Site Settings->Search->Result Sources
Ensure that “Local SharePoint Results” is the default. Not anything else.
Then try the search again, clicking everything will now show you files!