Can't connect Samsung S7 to Mac
Go to Settings -> SYSTEM(last tab in settings) -> About Device ->Tap on " Build Number" 7 times, this will enable developer mode.
Go back one screen and you have a new menu option for "Developer Option" tap that and turn on USB debugging.

Google for "Android File Transfer". Install and open the app, connect your phone to the mac.

a directory browser will show up and copying files is as easy and drag and drop.