1. Do you have the Android Auto tab turned on in Sync3? If you're not sure go to settings and look for the icon that says Android Auto. Open it and turn the switches on.
2. Have you checked your USB cable to be sure it can handle data? Try this. Connect your phone to a computer using the USB cable then see if you can find the phone's files on the computer. If the phone isn't showing up as a drive then the cable is bad or for charging only. Find a cable that'll let you transfer files from to and from your Samsung then head for the Edge.
3. Be sure Android Auto is running on the phone then connect to the USB port in the front center console cubby (other usb ports around the car won't work). A couple of things should happen. You'll be asked for data transfer permission on the phone's screen and (once you give permission) an Android Auto tab will be added to your list of selections (already includes audio, nav, phone, setup etc). Touch that new AA tab if the app hasn't automatically started.
BTW if you haven't already done so, turn on the 'new' Android auto by turning on the switch in AA's settings menu.