I readed this https://community.openproject.com/topics/5991

I modified the httpd.con for the subdomain in this way

Include /etc/openproject/addons/apache2/includes/server/*.conf
SuexecUserGroup "#501" "#501"
ServerName op.carletonita.com.ar
ServerAlias www.op.carletonita.com.ar
ServerAlias webmail.op.carletonita.com.ar
ServerAlias admin.op.carletonita.com.ar
DocumentRoot /home/carletonita/domains/op.carletonita.com.ar/public_html
#DocumentRoot /opt/openproject/public
######################################
#this options should help if the browser ends up with the error 502
SetEnv force-proxy-request-1.0 1
SetEnv proxy-nokeepalive 1
######################################
ProxyRequests off
Include /etc/openproject/addons/apache2/includes/vhost/*.conf
ProxyPass / http://127.0.0.1:6000/ retry=1 acquire=3000 timeout=600 Keepalive=On
ProxyPassReverse / “http://127.0.0.1:6000/”ErrorLog /var/log/virtualmin/op.carletonita.com.ar_error_log
CustomLog /var/log/virtualmin/op.carletonita.com.ar_access_log combined
ScriptAlias /cgi-bin/ /home/carletonita/domains/op.carletonita.com.ar/cgi-bin/
DirectoryIndex index.html index.htm index.php index.php4 index.php5
<Directory /home/carletonita/domains/op.carletonita.com.ar/public_html>
Options -Indexes +IncludesNOEXEC +SymLinksIfOwnerMatch +ExecCGI
allow from all
AllowOverride All Options=ExecCGI,Includes,IncludesNOEXEC,Indexes,MultiViews,SymLinksIfOwnerMatch
Require all granted
AddType application/x-httpd-php .php
AddHandler fcgid-script .php
AddHandler fcgid-script .php5
AddHandler fcgid-script .php5.6
FCGIWrapper /home/carletonita/domains/op.carletonita.com.ar/fcgi-bin/php5.6.fcgi .php
FCGIWrapper /home/carletonita/domains/op.carletonita.com.ar/fcgi-bin/php5.fcgi .php5
FCGIWrapper /home/carletonita/domains/op.carletonita.com.ar/fcgi-bin/php5.6.fcgi .php5.6
</Directory>
<Directory /home/carletonita/domains/op.carletonita.com.ar/cgi-bin>
allow from all
AllowOverride All Options=ExecCGI,Includes,IncludesNOEXEC,Indexes,MultiViews,SymLinksIfOwnerMatch
Require all granted
</Directory>
RewriteEngine on
RewriteCond %{HTTP_HOST} =webmail.op.carletonita.com.ar
RewriteRule ^(.*) https://op.carletonita.com.ar:20000/ [R]
RewriteCond %{HTTP_HOST} =admin.op.carletonita.com.ar
RewriteRule ^(.*) https://op.carletonita.com.ar:10000/ [R]
RemoveHandler .php
RemoveHandler .php5
RemoveHandler .php5.6
php_admin_value engine Off
FcgidMaxRequestLen 1073741824

NOTE: /home/carletonita/domains/op.carletonita.com.ar/public_html is a symlink to /opt/openproject/public, as you can see I tried too...

When I try op.carletonita.com.ar in my browser I just get:
Not found: /

I don't know about rubby and its context... But in the public folder of open project is nothing like index.* to apache start serving content...

I follow the directives to install in centos 7...

What more info you need to help me?