2015 WD 2TB My Passport Ultra

General info first.
I have two WD 2TB hard drives. Both were purchesed in 2015. Both were manufactued in Thailand. They bout have been used on a desktop and laptop bought in Thailand. Operating systems I use are Ubuntu15.05 on the desktop and Ubuntu14.04 on my laptop.

Today the hard drive I have, has one TB of TV shows on it. It would not mount on eather machine. Both hard dives work just fine untile today. Can someone please help me correct this mounting problem. Also exsplain why this might have happened?
Please be very careful with your repair sugestion as one TB of TV show is a lot and I would hat to lose that.

Are you able to test the unit on a different system? Perhaps, a different OS.

If possible, test the unit on a windows PC to test the unit using the DLG Tool.

I took a look around the internet and also was told to use a Windows OP to correct the problem. Bingo!! Fixed. Thanks