SSL configuration sends me to default NGINX page

I have followed the steps on: https://www.digitalocean.com/community/tutorials/how-to-secure-nginx-with-let-s-encrypt-on-ubuntu-16-04

I have no modified the Nginx default configuration other than changed the server name according to STEP 2 from the above instructions, using the main domain and the www version.

The rest remains as in: https://api.coderrocketfuel.com/assets/nginx-default-configuration-file.txt

The certifinate is for a subdoain. So in STEP5 I successfully obtained certificate for the subdomain

However, when I try to access subdomain it says:

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Welcome to nginx!

If you see this page, the nginx web server is successfully installed and working. Further configuration is required.

For online documentation and support please refer to nginx.org. Commercial support is available at nginx.com.

Thank you for using nginx.

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In the droplet I have an app developed with Vue.js installed on an Ubuntu 16

I was wondering if someone could help me with this, because there is something that I am missing.

thanks