Might be a typical hairpinning issue : your server cannot access itself via it’s public IP.
To confirm, paste here the output of :
curl yourdomain.tld
On my server I get :
<html>
<head><title>302 Found</title></head>
<body bgcolor="white">
<center><h1>302 Found</h1></center>
<hr><center>nginx/1.4.4</center>
</body>
</html>