Based on the link https://docs.bitnami.com/aws/how-to/generate-install-lets-encrypt-ssl/

For users with customed domain that is similar to my domain, chow.karmeng.my it is important to chane the –tls switch in the lego command into –http

sudo /opt/bitnami/letsencrypt/lego --http --email="youremail@yourdomain.com" --domains="domain.com" --domains="fancy.domain.com" --path="/opt/bitnami/letsencrypt" run