I have installed openproject on a Ubuntu server and  it  runs fine locally. I selected the default options during configuration. Thus a web server was installed and I do have an openproject.conf in the apache sites enabled. Http port 80 is opened for access from outside and I have a second webapplication being accessible from outside just fine. However, I can't reach openproject from outside. 

openproject.conf is in etc/apache2/sites-available and a symlink to it is in etc/apache2/sites-enabled

openproject.conf includes /etc/openproject/addons/apache2/includes/server/*.conf and includes /etc/openproject/addons/apache2/includes/vhost/*.conf

in openproject.conf DocumentRoot is set to /opt/openproject/public, the server name is set to servername

Locally I can start the openproject install with http://servername

When I try to start openproject through the internet, with http://server-IP/servername I get 404 not found. However, I do have another application on the same server with similar configuration which starts fine  using http://server-IP/alternative-servername (alternative-server name being the servername configured for the other application).

Which configuration details  am I missing?

Hi Ewald,

I'm not expert with that stuff, but usual, if you install a web-server local, it has no public access. You need DNS settings (https://superuser.com/questions/548300/how-can-make-a-web-server-publicly-accessible), otherwise the internet doesn't know your local machine... 
How, what you have done with your other "application" is not clear. There should be no solution to make web-servers public by just modifying an Apache config file!

thanks for your consideration. I will have a look at the link provided and let people know what the outcome is.