TLS-SNI-01 validation is reaching end-of-life. It will stop working permanently on March 13th, 2019.
Following an update I ran;
# certbot --version
certbot 0.10.2
https://community.letsencrypt.org/t/how-to-stop-using-tls-sni-01-with-certbot/83210
If the version is less than 0.28, you need to upgrade your Certbot.
Please advise