HomeKit AddOn | external Access

I tagged some items from OH2 so I can see and control them from HomeKit.
Everything works as supposed as long as I am on my home network. The Home App says, that my Apple TV 4 is connected properly.
But when I leave my home network, all my devices that come from OH2 show a status “updating” and after a timeout “no answer”. At the same time I can control my HUE devices and see HomeKit certified sensors without any issue.

Any idea?