all sites currently display this message when trying to access with https: //:
“Unable to access this site Pietramancini.com connection was denied.
Try it:

Check the connection
Check proxy and firewall
ERRCONNECTIONREFUSED ”

and

display this message when trying to access with http: //:
“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. ”

systemctl status nginx

● nginx.service - A high performance web server and a reverse proxy server
   Loaded: loaded (/lib/systemd/system/nginx.service; enabled; vendor preset: enabled)
   Active: active (running) since Wed 2019-09-25 14:27:15 -03; 1h 46min ago
     Docs: man: nginx (8)
 Main PID: 4562 (nginx)
    Tasks: 2 (limit: 2361)
   CGroup: /system.slice/nginx.service
           45─4562 nginx: master process / usr / sbin / nginx -g daemon on; master_process on;
           └─4565 nginx: worker process

Sep 25 14:27:15 ubuntu-s-1vcpu-2gb-nyc1-01 systemd [1]: Starting A high performance web server and a reverse proxy server …
Sep 25 14:27:15 ubuntu-s-1vcpu-2gb-nyc1-01 systemd [1]: nginx.service: Failed to parse PID from file /run/nginx.pid: Invalid argument
Sep 25 14:27:15 ubuntu-s-1vcpu-2gb-nyc1-01 systemd [1]: Started A high performance web server and reverse proxy server.

nginx -t

nginx: the configuration file /etc/nginx/nginx.conf syntax is ok
nginx: configuration file /etc/nginx/nginx.conf test is successful

thanks @ageorgiev