Help! My SD Card Not Mounting on MacBook

General
1

I am experiencing inconsistent SD card recognition on 2021 14" MacBook Pro’s built-in SD card reader.

Despite working flawlessly in a 2015 MacBook Pro, a Canon camera, and via a Thunderbolt adapter on the new MBP, 6 out of 8 SD cards (mix of brands/types) fail to mount on the built-in reader, triggering an “unreadable disk” error.

Attempts to fix via formatting (FAT, camera low-level format) and Apple Genius Bar support were unsuccessful.

2

Maybe the reasons are:

  • Firmware/driver bugs in the MBP’s SD reader.
  • Physical incompatibility with newer/high-capacity cards.
  • Faulty hardware in the built-in reader (e.g., inconsistent pin contact).

I suggested you can try these:

  1. Test with macOS Safe Mode to rule out software conflicts.
  2. Reset NVRAM/SMC to refresh hardware controllers.
  3. Check for macOS updates or beta patches addressing SD card issues.
  4. Use Disk Utility’s First Aid on the SD card while connected via Thunderbolt to check for hidden corruption.
  5. Contact Apple Support again with evidence of the issue (e.g., video of failure) to push for hardware diagnostics or a reader replacement.
3

I saw some users try using a USB-C reader the card appears to work perfectly.

Or continue using the Thunderbolt adapter for reliable access, as the built-in reader may have unresolved compatibility quirks.

You can read How to Fix the SD Card Not Mounting on Mac?

If all solutions fail, you’d better recover data with a professional tool like iBoysoft Data Recovery for Mac, then back up all the data, next, do a reformatting.