Use the following command to check and renew all installed Let’s Encrypt SSL certificates. You are able to automate the renewal by running the command as a cron job.
If you do want to renew a specific certificate manually, you can use
certbot certonly --force-renew and specify all of the associated domain names with
certbot certonly --force-renew -d example.com -d www.example.com
(if both of those names are part of the certificate).
As an alternative to specifying all of the names, you can run
certbot certificates to find out which certificates you have and what their names are, and then specify the certificate’s name with
certbot certonly --force-renew --cert-name example.com