Help - BT in car did not resume / play music

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Hello

 

iam a long time user of Poweramp. I like this so much, but i have this issue on all my cars.

My Huawei Mate RS is connected thru BT with my car. Works great with phone calls and playing Audio.
But on every connecting to my car, it starts Poweramp and play shortly music and stops immediately.

I setup up in Settings: Play at BT and under Audiofocus:: Resume on start. So all is set up for automating starting music on connecting BT.

In Lockscreen you can see, that Poweramps starts and plays for 2 seconds and stops.

So whatever i try to get it working, it fails. 

I have this on my new Mercedes E -Class and as well on on my Audi TT. All systems on car side are up to date.

Where is the trick?