Why can't my phone pass data to audio display?

[Android Central Question]

I just got a 2018 Honda Accord EX-L with Android Auto. I have a Samsung Galaxy S7 and when I plug in the USB cable it says "The connected device is unable to access data on this device." And then advises that an Android File Transfer or smart switch is required for Mac OS X devices. This makes no sense since both my phone and the audio display are android devices. Does anyone know what the problem is? I have tried removing and reinstalling the android auto app. Bought a brand new cable and no change.

 

[SpookDroid]

Check the Android Auto connection requirements for your car... is it supposed to work through USB? It might only be wireless, and when you plug the USB port on your phone, it tries to access data as if it were an USB drive (which you have to set your phone to Media Transfer for that to work; you should see a notification to select the mode when you connect the USB cable).

 

[Rukbat]

Even selecting MTP, the head unit would be looking at the root folder for music files, if the USB connection was for a USB drive or an .mp3 player. Since there aren't any (unless the phone has no SD card, and there are .mp3 files in the root of the internal sdcard folder), it won't find them.

Both Mac and Android run similar operating systems (BSD and Linux, respectively), so the head unit sees a Unix-like file system and assumes it's running Mac OS X.