Looking for help, cloudstack 4.2

[Nick de Bruijn]

Dear Cloudstack,
I just started using Cloudstack 4.2 for my school project, and I totaly love 
the way how you can manage your vm's by using Cloudstack.
As for now, I got everything up and running. But when ever I try to "view 
console" of an instance, it doesn't load the page, it leaves a blank page. Is 
this some kind of closed port problem?
I hope you can assist me and help me resolve this problem. I added a screenshot 
of how it looks.
Kind regards,Nick de Bruijn