Thanks for using Bitnami. Can you edit the crontab line to generate a new log file as shown below? Also note the cronjob will be run on the first day of the month, but that
lego doesn't allow you to renew the certificate if it is valid for more than 30 days yet.
0 0 1 * * /opt/bitnami/letsencrypt/scripts/renew-certificate.sh > /tmp/renew.log 2>&1
Apart from that, I see your website is using a valid Let's Encrypt certificate.