I am also having this problem. I bought a used 1TB My Passport that connects via UBS cord. I connected it to my system, and it says it's successfully installed, and that the device is properly working...
but I can't find it anywhere on my computer!
This is maddening, and I confess I am not a techie. I'm a mere mortal who would like to back up some files.
If anyone can explain to me how to get this running I will sing your praises!
I innocently purchased this thinking it would be easy to use. I see that I've stepped into a brand new nightmare...