No audio in Android Auto

[AC Question]

Yesterday I installed a new head unit in my car, a Pioneer AVH-4100NEX. So far everything works, I can talk to it and it does what I say, but there is no audio, when you ask it a question there's no reply, same with nav and phone calls. The weird thing is that Spotify playing through it works fine, so it is playing audio. My phone is a Nexus 6. Does anyone know how to fix this and what is causing it?

 

[dpham00]

Mod Note, I will move this to the n6 forums for more visibility