Update: I got it working!! Here's what I did:
I reinstalled Android Auto on the S8 (probably didn't need to do this, but I figured why not)
Used an Anker Powerline+ USB-C to USB 3.0 cable (3ft) directly connected to USB-2 on the receiver (yes, I know, that cable its not certified by Pioneer but the certified cables didn't work)
Reset the input settings on the Pioneer. Went from USB2 to HDMI and then back to USB2....and that did the trick!! Not sure why or how or whatever, but it's working. I tried the certified cables that I purchased last week just for giggles and they're still no good.