You may get an error No ssl_certificate in NGINX even anything in the access logs when attempting HTTPS on browser.  The http_ssl_module module aleady installed in NGINX,

We need to check in error log using tail command while attempting HTTPS ,

# tail -f /var/log/nginx/error_log

2014/01/02 15:23:18 [error] 893#0: *71 no "ssl_certificate" is defined in server listening on SSL port while SSL handshaking, client:, server:

You should need to add following lines to NGINX configuration file.

server {
ssl on;
listen 80;
listen 443 ssl;
return 301 $scheme://$request_uri;

Note : Also check and set your SSL Cert. file path in configuration.