found out the problem. i have a 2006 dodge charger. it has a factory amp. sooooo..
Since you're reusing the factory amp. The factory amp only takes in a stereo signal and then outputs the 6.1 signal to the 7 speakers. The stereo input of the amp matches directly up with the rear input wires on the deck. So the head unit won't send the Bluetooth or nav prompts through the rear speakers for obvious reason that you're not in the backseat using those features.
So you need to have the installer switch the white and gray wires to the green and purple. No need to hook up the rears off the dec