Due to a bug that’s been fixed in newer versions of Certbot, /etc/letsencrypt/renewal/s1.prismforge.com.conf is missing one of the settings.
It might work to run “certbot renew --cert-name s1.prismforge.com -w /insert/path/here” with the correct web root path.
If not, try repeating the command you used to create the certificate originally – e.g. “certbot certonly --webroot -d s1.prismforge.com -d admin2.prismforge.com -w /insert/path/here” or whatever.