Saving debug log to /var/log/letsencrypt/letsencrypt.log
Certbot failed to authenticate some domains (authenticator: nginx). The Certificate Authority reported these problems:
Domain:
Type: serverInternal
Detail: During secondary validation: Remote PerformValidation RPC failed
Hint: The Certificate Authority failed to verify the temporary nginx configuration changes made by Certbot. Ensure the listed domains point to this nginx server and that it is accessible from the internet.
Failed to renew certificate with error: Some challenges have failed.
All simulated renewals failed.
1 renew failure(s), 0 parse failure(s)
Ask for help or search for solutions at https://community.letsencrypt.org. See the logfile /var/log/letsencrypt/letsencrypt.log or re-run Certbot with -v for more details.
That is an unusual error. Do you limit access to your server by country or geography? Because Let's Encrypt recently started using more points around the world to validate from. Seeing "Seconday validation" in the error message means this might be happening to you.
People who previously only allowed USA (and their home countries) would no longer work.