Unity - Oculus Gear Vr - Android - Integration - UnityPlayer.UnitySendMessage not working

I have two projects. They are exactly the same, except that one of them is set up for the Oculus Gear Vr...

Then I export both of these Projects and open them as AndroidStudio Projects.

When i run these now both work exactly as expected.

But when i try to use the UnityPlayer.UnitySendMessage - method, the method seems not to be executed in the app with the setup vor VR...

The app doesnt crash, it doesnt show any errors in LogCat and i tried to catch any Throwable but that didnt work either...

(On the App with no VR setup the exact same lines of codes works ...)

I would appreciate any help :D