If your external hard drive is not showing up after the macOS "Tahoe" update (assumed to be a future or fictional version beyond known releases), the issue likely stems from changes or bugs introduced during the update. This is not uncommon after macOS upgrades, which can impact hardware compatibility, drivers, and system permissions. Here are several key reasons why your drive might not be appearing, and what you can do to resolve the issue:
1. Drive Format Incompatibility
One of the most common reasons a drive fails to mount is that it's formatted in a file system no longer fully supported or deprioritized by macOS after an update. For example:
NTFS (Windows format): macOS can read NTFS drives but does not write to them without third-party tools. An update might have removed or broken these tools.
Older formats (FAT32, exFAT, HFS+): If your drive uses an outdated format, the update may require additional steps or reformatting to re-enable compatibility.
Solution: Open Disk Utility (Applications > Utilities > Disk Utility) to check if the drive is recognized but not mounted. If it's listed but greyed out, try manually mounting it. If not, you may need to reformat it—but only after backing up the data on another machine if possible.
2. System Permissions and Privacy Changes
macOS updates often increase system security. "Tahoe" may have introduced stricter permission controls, especially around accessing external media.
Solution:
Go to System Settings > Privacy & Security > Full Disk Access and make sure Finder or third-party file browsers have proper permissions. You might also need to allow USB accessories in Settings > Privacy & Security > Accessories.
3. Faulty or Missing Drivers
The update may have removed or disabled third-party drivers (e.g., for NTFS or proprietary hardware). Some drives from Seagate, Western Digital, or LaCie rely on manufacturer-specific drivers or encryption software.
Solution:
Check the manufacturer’s website for updated macOS "Tahoe" drivers or utilities. Reinstall them if needed.
4. USB/Thunderbolt Port or Cable Issues
Sometimes the issue is hardware-related, but it surfaces conveniently after an OS update, making it look like a software issue.
Solution:
Try a different port or cable.
Test the drive on another computer.
Use a powered USB hub if the drive isn’t self-powered.
5. macOS System Bugs or Glitches
Occasionally, macOS updates introduce bugs that affect drive mounting, especially if APFS (Apple File System) is involved.
Solution:
Restart your Mac with the drive connected.
Reset NVRAM/PRAM and SMC (if applicable).
Boot into Safe Mode and see if the drive appears.
Use Terminal to check with
diskutil listand try mounting the drive manually.
6. Drive Corruption
The update process might have interrupted or affected the drive’s file system, making it unmountable.
Solution:
In Disk Utility, use First Aid on the drive. If that fails, recovery software (like Disk Drill, Stellar, or Data Rescue) may help retrieve the data.
Final Thoughts
If none of the above works, it's worth checking with Apple Support or visiting a Genius Bar. When macOS updates like "Tahoe" introduce major changes under the hood, especially related to file system architecture or security frameworks, issues like these are unfortunately common. Regular backups and checking for compatibility before updating are the best long-term safeguards.