Setting search criteria for finder issue

Can you help? I'm having problems setting search criteria for finder issue. If I searched If I search "this Mac" it searches and finds all the files with the keyword just fine.

If I narrow it down to a folder, then I get nothing. See the screenshot below. My project folders are held on Dropbox but when I do the search the entire market doesn't seem to have a problem finding them. Just wondering if this is part of the issue. Any help appreciated