It is regular Bluetooth communication. However, from logs that you provided everything looks OK. If Android Auto did not start there is a matter of phone. Samsung phones have also many weird policies for networking and security that causes a lot of problems. S9 is one of our reference phones and we did not observe any similar problems during testing. In your case it looks like an issue with connecting to the WiFi Hotspot. Are you in range of another WiFi network (with internet access) when you are testing wireless AA? Please try to unpair and pair with Raspberry PI and reset network settings on the phone.