Configuration problem: request default 15.15.15.15/ not working

[Frank_Mascarell]

I've also tried adding "/" and throwing the same error. I have also added to
the .conf file:

location = / {
        include proxy_params;
        proxy_pass http://unix:/run/gunicorn.sock;
}

before the fragment location / {......} with the same error. 
This error is very strange. The configuration is very simple, but I can not
find the problem.

Posted at Nginx Forum: https://forum.nginx.org/read.php?2,281393,281411#msg-281411