Hey, I actually just discovered this headunit app recently and bought it. I was attempting to troubleshoot "communications error 7"
I wasn't really sure if there was a definitive fix for this issue but I just thought I would throw this in here to see if anyone knew why I'm getting it.
I'm using the recommended OTG cable
on a unrooted nexus 5x on android oreo trying to use the 2013 nexus 7 as the headunit 6.0.1 , ive tried both the phone and the tablet android auto apps in developer mode too.
There is actually a security update for my nexus 7, which I'm going to run to see if that changes anything
Edit: whoops! just went one page back and read about the new developer... i'll be sending a pm