I just plugged in my external hd via USB for a Time Machine backup. However it will not mount.

enter image description here


  • Unplugged the hd
  • Restarted the computer
  • Plugged it back in

When I do this, Disk Utility spins and won't load. So I then:

  • Unplug the disk
  • Open Disk Utility
  • Plug in the disk and that shows the image above

When I press mount, it says the disk is already unlocked. However it will not show up.

This started after I tried repairing the volume, but it wouldn't repair. Now I can't select it.

Any options at this point other than erasing the whole HD and starting over?

  • same problem here, did you find a working solution?
    – iGenio
    Commented Jun 23, 2021 at 13:23

2 Answers 2


I've had problems like this also. If you have multiple USB ports try using a different port. Also try using a different cable and a different port.

You don't want to use a flaky drive for your backup. So, yes it seems like reformatting the drive and starting over makes sense, or replace it.


The drive repair function in Disk Utility is and always has been mostly useless. If you really want to repair a drive (with software problems, not hardware problems of course), you need a program like Disk Warrior.

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