Fusioncharts not displayed in production

I have two Qnap NAS servers hosting my scriptcase production applications. My problem is that fusioncharts are not displayed on the newest Qnap server. On the old server and on development everything works fine. So my conclusion is that my problem is caused by the server configuration of my newest Qnap. I am investigating /mnt/HDA_ROOT/.config/apache/apache.conf but I cannot find the problem. Any suggestions will be highly appreciated.

Roelof