I meet issue on OMV 4.X.
phpvirtualbox small preview box can see vm is running, but CONSOLE tab cannot see anything. I test it with Chrome, Firefox, IE, IE edge. Nothing work.
Besides, I can use realvnc to connect to vm (192.168.1.131:9001) without error, but no images show up and show all black on realvnc screen. At this time, keyboard is working. I can type in something and see it from small preview box although preview is really small.
With this tiny small preview window, no one can really install anything on it !!
It seems nobody wants to handle it.
I saw a lot of same issues reported starting from 3.x, 4.x, and also 5.x