Vertical Position - Above Ground Estimate Error


today i tried to fly my plane in FBWA, but the problem is that it doesnt accept any throttle, even though it is armed.
The interesting thing is that all pre arm checks pass with no problem at all, but i can only use the throttle in manual.
After looking in the Tower App, i saw a red cross under “Vertical Position - Above Ground Estimate”.
I dont know if this is the problem, because after intense googling i couldnt find any further information regarding this problem. GPS and Baro work just fine, Terrain following is also disabled.
Maybe you got an idea.

Greetings and thanks for any help