Use the following command to force renewal of LetsEncrypt Virtualizor certificate:
/usr/local/emps/bin/php /usr/local/virtualizor/scripts/virt_acme.php --renew --force -d {DOMAIN NAME}
For example:
/usr/local/emps/bin/php /usr/local/virtualizor/scripts/virt_acme.php --renew --force -d servername.domain.com