I was originally trying to have https with Positive SSL from Namecheap/Comodo.

I thought I have all the things done correctly but when I try 'sudo service apache2 restart', it just says [OK] but https is still not working

When I try

$ openssl x509 -in /etc/ssl/robobu.io.crt -noout -modulus | openssl sha1 openssl rsa -in /etc/ssl/robobu.io.key -noout -modulus | openssl sha1

openssl: No such file or directory
rsa: No such file or directory
-in: No such file or directory
-noout: No such file or directory
-modulus: No such file or directory
(stdin)= YYYYYYYYYYYYY

the modulus of the certificate XXXXXXXXXXXXXXX and modulus of the private key YYYYYYYYYYYYYYY do not match.

${APACHELOGDIR}/error.log

[Mon Nov 09 02:11:35.854042 2015] [mpm_prefork:notice] [pid 26088] AH00169: caught SIGTERM, shutting down
[Mon Nov 09 02:12:11.994884 2015] [ssl:emerg] [pid 26503] AH02240: Server should be SSL-aware but has no certificate configured [Hint: SSLCertificateFile] ((null):0)
[Mon Nov 09 02:12:11.994972 2015] [ssl:emerg] [pid 26503] AH02312: Fatal error initialising mod_ssl, exiting.
[Mon Nov 09 02:13:59.088969 2015] [mpm_prefork:notice] [pid 26619] AH00163: Apache/2.4.7 (Ubuntu) PHP/5.5.9-1ubuntu4.7 OpenSSL/1.0.1f configured -- resuming normal operations
[Mon Nov 09 02:13:59.089091 2015] [core:notice] [pid 26619] AH00094: Command line: '/usr/sbin/apache2'
[Mon Nov 09 02:27:40.708424 2015] [mpm_prefork:notice] [pid 26619] AH00169: caught SIGTERM, shutting down
[Mon Nov 09 02:27:41.734314 2015] [mpm_prefork:notice] [pid 26851] AH00163: Apache/2.4.7 (Ubuntu) PHP/5.5.9-1ubuntu4.7 OpenSSL/1.0.1f configured -- resuming normal operations
[Mon Nov 09 02:27:41.734409 2015] [core:notice] [pid 26851] AH00094: Command line: '/usr/sbin/apache2'

my apache2.conf is

ServerRoot "/etc/apache2"
Mutex file:${APACHE_LOCK_DIR} default
PidFile ${APACHE_PID_FILE}
Timeout 300
KeepAlive On
MaxKeepAliveRequests 100
KeepAliveTimeout 5
User ${APACHE_RUN_USER}
Group ${APACHE_RUN_GROUP}
HostnameLookups Off
ErrorLog ${APACHE_LOG_DIR}/error.log
LogLevel crit
IncludeOptional mods-enabled/*.load
IncludeOptional mods-enabled/*.conf
Include ports.conf

******
<VirtualHost *:80>
   ServerAdmin webmaster@Robobu
   DocumentRoot /var/www
   Servername  128.199.71.225
   ServerAlias Robobu www.Robobu
</VirtualHost>

and /etc/apache2/sites-available/000-default.conf is

<VirtualHost *:80>
    ServerName robobu.io
    Redirect permanent / https://robobu.io/
</VirtualHost>
Listen 443
<VirtualHost *:443>
    ServerAdmin webmaster@localhost
    DocumentRoot /var/www/html
    ServerName robobu.io
    SSLEngine on
    SSLCertificateFile /etc/ssl/robobu.io.crt
    SSLCertificateKeyFile /etc/ssl/robobu.io.key    
    SSLCertificateChainFile /etc/ssl/robobu_io.ca-bundle
    ErrorLog ${APACHE_LOG_DIR}/error.log
    CustomLog ${APACHE_LOG_DIR}/access.log combined
</VirtualHost>

# vim: syntax=apache ts=4 sw=4 sts=4 sr noet

my server is Server version: Apache/2.4.7 (Ubuntu) and using WORDPRESS

I contacted Namecheap online chat support but the person eventually said "I can advise you to contact your hosting provider for the further investigation. It seems the errors it mod_ssl can prevent you from connecting via 443 port."

I originally followed How To Install an SSL Certificate from a Commercial Certificate Authority and now have no idea where to fix...