If you may get an error after configured SSL or installed ssl_module for your apache server, you had an extra Listen 443 in httpd.conf or conf.d/ssl.conf file. So you need to remove from any one configure

# systemctl status httpd.service



httpd.service - The Apache HTTP Server

Jan 19 12:00:09 host.thelinuxfaq.com httpd[6136]: (98)Address already in use: AH00072: make_sock: could not bind to address [::]:443

Jan 19 12:00:10 host.thelinuxfaq.com systemd[1]: httpd.service: main process exited, code=exited, status=1/FAILURE

Jan 19 12:00:10 host.thelinuxfaq.com systemd[1]: Failed to start The Apache HTTP Server.

Jan 19 12:00:10 host.thelinuxfaq.com systemd[1]: Unit httpd. Find the ssl port number :443 in configure files,
# grep '443' /etc/httpd/conf.d/*


/etc/httpd/conf.d/ssl.conf:Listen 443 https

/etc/httpd/conf.d/ssl.conf:<VirtualHost _default_:443>

/etc/httpd/conf.d/ssl.conf:#ServerName www.example.com:443


finally start your apache server,
 
# service httpd start

Check whether the both port :80 and:443 are pointing to your httpd,
 
# netstat -anp | grep httpd


tcp6       0      0 :::443                  :::*    LISTEN      7291/httpd

tcp6       0      0 :::80                   :::*    LISTEN      7291/httpd

unix  3      [ ]         STREAM     CONNECTED     5088028  7291/httpd