macOS "The disk you attached was not readable!"

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Hey everyone,
I have a Sandisk 1T SSD, external drive to an iMac (Big Sur 11.7) that just started giving me this message. The Sandisk is less than 1 year old and has been working fine till now. it’s formatted as Exfat. This drive has lots of important stuff on it. Is there any way to bring it back to life? I’ve tried a different USB port, and tried restarting the iMac. - Thanks

mac error
mac error273×290 34.2 KB

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Hi @GEORGEHegele ,

Have you opened a Support Case? If not opened, for more information, please contact the SD Technical Support team for best assistance and troubleshooting:
https://kb.sandisk.com/app/ask

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Unfortunately, this error on your Mac can be triggered by a variety of reasons. For example, has the external drive been dropped recently? Or did you just update your macOS? This article provides seven solutions for the ‘The disk you attached was not readable by this computer’ error. Hope it helps. If the hard drive contains important data, you can try using a professional Mac recovery tool or contact a data recovery service.

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The disk you attached was not readable by this computer," it indicates potential problems with the external disk’s format or compatibility. To resolve this issue, follow these steps:

  1. Use Disk Utility (Mac)
    Open Disk Utility and check if the SD card appears on the left side. If it does but can’t be mounted, right-click on the SD card and select “Mount.”
    If the disk is listed but grayed out, this may signal a format issue.
    If the card remains unmountable or Disk Utility reports a file system error, consider formatting the external drive (note: formatting will erase all data on the SSD, so it’s recommended to use data recovery software to retrieve files before proceeding).
  2. Use Disk Management (Windows)
    Right-click on the Start menu and select “Disk Management.” Look for your external disk. If it’s listed but shows as unallocated or doesn’t have a drive letter, it may need initialization or a drive letter assigned.
  3. Update Drivers and Run First Aid (Mac)
    If the previous steps don’t help, try updating your Mac’s drivers. After that, run First Aid in Disk Utility to fix the unreadable disk (refer to detailed instructions if necessary).
  4. Contact Manufacturer Support
    If none of the above methods work, contact the manufacturer’s support team for further assistance. They may provide specific troubleshooting steps or suggest repair/replacement options.