add new Certbot Directory - https://github.com/certbot/certbot/blob/master/CHANGELOG.md

server/lib/classes/letsencrypt.inc.php

@@ -266,7 +266,7 @@ class letsencrypt {
 				$app->log("Create Let's Encrypt SSL Cert for: $domain", LOGLEVEL_DEBUG);
 				$app->log("Let's Encrypt SSL Cert domains: $cli_domain_arg", LOGLEVEL_DEBUG);
 			
-				$letsencrypt = explode("\n", shell_exec('which letsencrypt certbot /root/.local/share/letsencrypt/bin/letsencrypt'));
+				$letsencrypt = explode("\n", shell_exec('which letsencrypt certbot /root/.local/share/letsencrypt/bin/letsencrypt /opt/eff.org/certbot/venv/bin/certbot'));
 				$letsencrypt = reset($letsencrypt);
 				if(is_executable($letsencrypt)) {
 					$letsencrypt_cmd = $letsencrypt . " certonly -n --text --agree-tos --expand --authenticator webroot --server https://acme-v01.api.letsencrypt.org/directory --rsa-key-size 4096 --email postmaster@$domain $cli_domain_arg --webroot-path /usr/local/ispconfig/interface/acme";