Cheap Android Head Unit

Img from ebay

I bought this unit from ebay to install in my car. I tried to root it to update the Boot img and animation. I got root using KingRoot but couldn’t get the animation to show. I unrooted and restored.
I have it installed in my car now with an external microphone connected to the 3.5mm AUX port on the back which was marked for MIC on the sticker on the bottom of the unit. The mic is not working, when I call or people call me they cannot hear me.