'The disk you inserted was not readable by this computer' is a common error that happens on macOS. As a result, you can't access all the files on your micro SD card including your precious videos. Luckily, you can see the micro SD card's name shows up under External in Disk Utility. Though the SD card name is gray, you can still have a chance to access it and have a look at your video.
First, Open Disk Utility, select your gray SD card, and click on the "Mount" button at the upper menu bar. If the SD card not mounting on Mac Disk Utility still, it means your micro SD card may have some little problems. You can use Disk Utility First Aid to repair SD card and make it readable:
- In Disk Utility, click Show All Devices in View option and select your SD card in the left sidebar.
- Click First Aid in the top menu of Disk Utility.
- Click Run to check and repair errors in this drive.
If unfortunately, you still can't access the micro SD card after running First Aid, the SD card may have been damaged severely. To make it usable again, you need to format the SD card. However, as reformatting will erase all data on it, you should recover the inaccessible videos first. Here it's highly recommended to retrieve your video with iBoysoft Data Recovery for Mac.
Here's how you can restore your data on the micro SD card with the help of iBoysoft video recovery software:
Step 1: Free download and install iBoysoft Data Recovery for Mac.
Step 2: Launch the recovery app, select the unreadable micro SD card and click "Search for Lost Data".
Step 3: Preview the found files and check the boxes before the video files you want to recover, then hit the Recover button and save them on your Mac computer.
Now, if you're sure that you've got all your wanted videos stored on your Mac, you can format the micro SD card on Mac Disk Utility. Thus, the disk unreadable error on Mac should be fixed also. The next time you insert your SD card on your Mac, it won't give you an error prompt.
