There can be problems with SD card slots not working properly. Users cannot get access to files stored on their SD cards, although the latter seem to be undamaged. If reinserting a card and restarting a computer does not help, you should start with determining the cause of this issue. It is not necessarily related to the SD card slot.
First of all, make sure you insert your card properly. The metal contacts must face down and point toward your Mac. Put the card in carefully, but not too slowly: sometimes it does not mount properly because of it.
Having another SD card for a test significantly simplifies the task. But if you do not have it, the first solution is to launch the Image Capture app before inserting a card.
If it does not help, there may be problems with contacts. Try inserting a card leaving a part of it outside, and then lift it up a bit with a little pressure.
You should also make sure the contacts on your card are clean. Rub them lightly with a new pencil eraser. Then open a card up and clean internal contacts.
If this approach is not successful, try the following steps.
Using Disk Utility
With Disk Utility, you can find out if a card is recognized by your computer.
In case the card won’t show up in the system, there may be an issue with the card slot, or with the card itself, which is more likely. Then you should return it for warranty replacement.
If you see the card in Disk Utility, try recovering it, since it may be corrupted.
- Open the Disk Utility program by typing its name in Spotlight and double-clicking the search result. You can also locate it with Finder. Click on the Finder icon, open the Applications folder and choose Disk Utility.
- Click once on the SD card’s icon.
- Go to the First Aid tab, and then click the Repair Disk
- You will see a progress bar filling in.
- Quit Disk Utility when the recovery process is complete.
- Delete the card’s icon from the desktop and pull your card out of the SD card slot.
- Pull it in again and see if you can access files stored on the card.
Resetting the SMC
Try resetting the SMC (System Management Controller), if you still experience problems. Apple suggests doing this if your Mac does not recognize external devices.
If you use a MacBook laptop:
- Shut down your computer.
- Simultaneously press Shift + Control +Option key combination and the power button.
- Release them after 10 seconds.
- Then press the power button again to boot your Mac.
If you use a Mac desktop computer:
- Shut down your computer and then unplug it from the power source.
- Plug it again after 15 seconds.
- Press the power button after 5 seconds to boot your Mac.
If you use an iMac Pro:
- Shut down your computer.
- Press the power button and hold it for 8 seconds.
- Then release it and wait for 10 seconds.
- Press the power button to boot your computer.
Contact Apple support if nothing helps.