I have been spending few hours on that issue and despite the high number of posts related to it, I cannot solve it. I have a Fedora 20 box with Nginx + PHP-FPM that worked q
I ran into the same problem, and after trying all the suggestions above it still didn't work. Then I checked my files. Obviously I am not a server expert.
It turned out I have a folder /sites-available and /sites-enabled. I had updated the default file in the sites-available folder but not in the /sites-enabled folder. After doing that (and a restart of nginx), it all started to work.
Took me some time to solve this, I hope this helps someone else to fix it sooner.