In my error log i get
[emerg] 10619#0: a duplicate default server for 0.0.0.0:80 in /etc/nginx/sites-enabled/mysite.com:4
on Line 4
If you're on Digital Ocean this means you need to go to /etc/nginx/sites-enabled/ and then REMOVE using rm -R digitalocean and default
It fixed it for me!
Pic of Console on Windows 10 using Bitvise