How old is the drive? I have gone through several external drives over the years because after about three years they stop working – not accessible, just as shown in your images. I don’t use them any more, instead I invest in high capacity internal drives (3TB), and rely on online backup in case they go south, which so far they have not.
A friend tried Testdisk and found it wanting. They used http://www.eassos.com/eassos-recovery.php to get their data back. I have since recommended it to another friend who experienced the same problem and it got back nearly the entirety of their data.