creating a configuration file symbolic link

sudo ln -s /etc/apache2/sites-available/default-ssl.conf /etc/apache2/sites-enabled/000-default-ssl.conf

Enable SSL for apache server in 5 minutes

add this to 000-default-le-ssl.conf

ServerName example.com
ServerAlias www.example.com

https://community.letsencrypt.org/t/cant-renew-certificate-we-were-unable-to-find-a-vhost-with-a-servername-or-address/11675/2