If you have bellow error you should install mod_ssl
“Invalid command “SSLEngine”, perhaps misspelled or defined by a module not included in the server configuration”
The error message indicates that the module mod_ssl required to run SSL engine on a CentOS server is missing and needs to be installed.
Install the mod_ssl module using yum
yum install mod_ssl
Once it is installed, make sure to restart the Apache service
service httpd restart