You'll have to help me out a bit more here.
If you access your public IP address, do you see the default page? If you try to access the domain name, what do you see? Does the domainname resolve to your ip address?
Can you configure a static page for the vhost first? ie try something like https://www.digitalocean.com/community/tutorials/how-to-set-up-nginx-server-blocks-virtual-hosts-on-ubuntu-16-04 .