Nginx not serving site unless index.html not mentioned in URL

This is probably something very trivial. But I can't seem to get Nginx to serve index.html if I just enter the IP-address in the browser's address bar (for example: 194.XXX.YYY.ZZZ)

To serve index.html, I have to explicitly type 194.XXX.YYY.ZZZ/index.html. If I don't, I just see Nginx's default welcome page

Below is my nginx .conf file. Have I made an obvious mistake? Or, have I missed something?

Thanks for your help, Abhinav

    1 
    2 server {
    3     listen         80;
    4     listen         [::]:80 ;
    5     server_name    194.XXX.YYY.ZZZ;
    6 
    7     location / {
    8       root /home/admin/fe/sandbox/current/web/;
    9       index index.html;
    10     }
    11 
    12     gzip             on;
    13     gzip_comp_level  3;
    14     gzip_types       text/plain text/css application/javascript image/*;
    15 }