Apache httpd does not load index.html when a web app is installed

In a CentOS 7 installation I installed OrangeScrum (which is a standard PHP application copied to /var/www/html). When I type the server IP I get the Apache test page and if I have an index.html page it will be displayed. And when I type the server-ip/orangescrum for example I get the web app. All this is fine. Moving on to a server with Scientific Linux 7 I did the same, but when I install the app to the Apache and typing the server ip alone I get the app itself not the Apache status nor the index.html if any. Nothing has been done to httpd.conf except adding a virtual host definition like here What am I missing to do in order to get the root index or the Apache test pages to work?