So i bought this http://Ultra Fit and it worked fine on my Mac, formatted it to exFat and it was working fine with my PC. However a few days ago it started to not showing up. I would have to plug it out and in 10 times before it worked, but sometimes it worked in one go. Its really weird and now its not even showing up on any PC. I re-formatted it yesterday on my laptop and took it out and plugged it back in and it didn't show up again. What can i do?