When I first plugged in my WD Passport, I was able to see the drive icon on the desktop of my Macbook. Then, they asked if I want to use it as backup so I agreed. They said that I will need to delete all content in my hard disk and I agreed since there are no files in it. Then, the process was unsuccessful and after that I can no longer see my external drive on the desktop, but I can still see it under Disk Utility. Anyone knows how to solve this?
If you can see it within Disk Utility then try formatting your unit to HFS+ since the unit may have lost its file system.
If the unit can not be formatted then it is defected and should be replaced under warranty (Which would explain the previous failed attempt).