After setting SSL in the Apache default-ssl.conf file I was not able to access the website using https which was showing ERR_SSL_PROTOCOL_ERROR.
Also the curl command was showing the following error:
curl: (35) error:1408F10B:SSL routines:ssl3_get_record:wrong version number
Fix:
sudo a2ensite default-ssl
and restart apache2.
Note: Before that you need to ensure following modules are also enabled in apache.
sudo a2enmod ssl
sudo a2enmod headers
sudo a2enconf ssl-params