Sorry just bumping this.
I have dug around some more and I get the following error in the nginx error logs:
2017/05/23 21:49:25 [error] 1134#1134: *72 upstream timed out (110: Connection timed out) while reading response header from upstream, client: 127.0.0.1, server: , request: "GET / HTTP/1.1", upstream: "http://127.0.0.1:5000/", host: "127.0.0.1"
It is also perhaps worth noting that it just started working the other day until I once again had to restart my server.
I really can't find any reason why this could be happening. This is a vanilla install.