Vestacp Nginx proxy passing to a node application

Hello DO Community, I hope all of you are doing great.

I am facing an issue with nginx proxy passing. So far I have successfully install Ubuntu 14.04 and vestacp panel and they are working great. I can even create sub-domains with no problem.

Now I want to create a ghost blog in a sub-domain (eg blog.main-doimain.com) which by the way runs on node. I have managed to run the ghost blog on port 3000 and i can access it using main-domain.com:3000

To access it via sub-domain I have added following server block on nginx (which is installed by vestacp)

server {
    listen 80;
    server_name blog.main-domain.com;

    root /var/www/ghost;
    index index.html index.htm;

    location / {
        proxy_pass http://127.0.0.1:3000;
    }
}

but still i can’t access it.

Then I created a blank droplet, installed ubuntu 14.04, installed nginx (only) then installed ghost in it in the same way and added the above server block. And surprisingly it worked, I could access it like blog.main-domain.com!!!

My question is:

1. Am I doing something wrong??
2. Does vestacp & ghost work along side this way or not??
3. Has anyone tried something like this and succeeded or failed??

Thank you and sorry for really long post.