SSL not enabled on nginx even with cert successfully installed

Question

I have a site running on a nginx server. I am trying to enable ssl. I have downloaded the cert and have the following output as per this guide: https://www.digitalocean.com/community/tutorials/how-to-secure-nginx-with-let-s-encrypt-on-ubuntu-16-04. But when I go to https://example.com it does not work... what am I missing?

root@host2:~# certbot certificates

Saving debug log to /var/log/letsencrypt/letsencrypt.log

    -----------------------------------------------------------------------------
    Found the following certs:
      Certificate Name: example.com
        Domains: example.com
        Expiry Date: 2017-11-25 05:49:00+00:00 (VALID: 89 days)
        Certificate Path: /etc/letsencrypt/live/example.com/fullchain.pem
        Private Key Path: /etc/letsencrypt/live/example.com/privkey.pem
    -----------------------------------------------------------------------------

By not working, I mean that when I go to the http version, the site loads fine but when I go to the https version, it says the site cannot be reached.