I have had the same issue with two different My Passport for Mac drives now from WD. Neither have been recognised my machine or have been recognised intermittently.
This has left me going months without a backup of my machine
I have tried using different cables and different computers to no avail
I cannot even see the drive in disk utility to reformat it
I have had 4 RMAs now with WD and the issue is still not fixed, it seems like a root fault with the firmware in the drive rather than an issue with my particular
drives being faulty
Has anyone experienced a similar issue, or can anyone help me with a solution??