Samsung galaxy s6 screen is completely black. Everything else is fully functional. When I turned on the phone I could hear apps opening. The digital buttons beside the home button lights up, volume buttons working. Only problem is that the screen is black
Either the connection to the display has come loose, or there is damage to the display (even if you can't see any). If under warranty, I would contact the manufacturer. If not, you can try replacing it yourself or take it to a local tech.