Certbot failed to authenticate some domains (authenticator: nginx)

Certbot failed to authenticate some domains (authenticator: nginx). The Certific ate Authority reported these problems:
Domain: example.com
Type: connection
Detail: : Fetching http://example.com/.well-known/acme-challen ge/jV2_e26mL2o8BO8lsapYI1JOpoPa8QvKcphVKaPjK_s: Connection refused

Hint: The Certificate Authority failed to verify the temporary nginx configurati on changes made by Certbot. Ensure the listed domains point to this nginx server and that it is accessible from the internet.

Some challenges have failed.
Ask for help or search for solutions at https://community.letsencrypt.org. See t he logfile /var/log/letsencrypt/letsencrypt.log or re-run Certbot with -v for mo re details.

How can i resolve it?

To use the --nginx plugin you must have a working nginx server for HTTP (port 80). The "connection refused" means something on your setup is blocking the Let's Encrypt server from connecting to your nginx. Possibly a firewall, or a router or wrong port / NAT routing. If that is your real IP address you should check your AAAA IPv6 address too.

We can only give general advice unless you provide specific info such as your domain name and the other answers to the form you were shown.

The Let's Debug website is helpful to debug new setups