Check Finder → Settings → General / Sidebar to show external disks, open Disk Utility (View → Show All Devices) and click Mount, run First Aid, and try another cable, port and adapter. NTFS drives mount read-only on Mac.

The short explanation

If Disk Utility lists the drive, it’s detected and the problem is mounting, formatting or Finder visibility. If it’s not listed at all, the cable, port, hub or drive power is the problem, or the drive has failed.

What you'll see

  • Drive doesn't appear on the desktop or Finder sidebar.
  • Disk Utility shows it greyed out.
  • Can read but not write files (NTFS).

What causes it

  • Finder settings hiding external disks.
  • Unmounted or corrupted volume.
  • Unsupported format (NTFS write).
  • Cable, port, hub or power issues.

How to fix it

  1. Finder settingsFinder → Settings → tick External disks in General and Sidebar.
  2. Mount in Disk UtilityDisk Utility → View → Show All Devices → select the volume → Mount.
  3. Run First AidSelect the volume → First Aid.
  4. Check connectionsTry another cable/port, avoid unpowered hubs, use the drive's power adapter if it has one.
  5. FormatsNTFS is read-only; exFAT works on Mac and Windows. Reformatting erases data, so copy files off first.
  6. Check System InformationApple menu → About This Mac → More Info → System Report → USB/Thunderbolt to see if it's detected.
How to confirm the fix: The drive appears in Finder and you can open files.

Stop it happening again

Eject drives before unplugging and use exFAT for cross-platform drives.