Node red iframe - vnc

I posted before about controlling my displayed webpage by mqtt.
The solution was to use the iframe node. Now i finally got it working. ( i thought ) but it only displays the correct page in vnc. But if i look on the connected screen the screen stays black. If i open nodered.org for example it displays the page on physical and on vnc correct.

Anyone an idea why it works on vnc and not with a physical screen?

Unfortunately the page is from a local game controller so i cannot share the link of the page were it is about

Update
If i open a browser manual on the pi the page is displayed correctly :grimacing: