Given on your situation, you should use professional SD card recovery software such as iBoysoft Data Recovery for Mac to recover data from an unreadable microSD card. After SD card recovery, you can format the unreadable SD card to start over again.
Based on your description, your SD card is formatted with FAT32, which is able to work in macOS, and First Aid does not help fix the SD card not reading on Mac issue. It's possible your SD card has severe issues that First Aid fails to repair. In this case, you can format the memory card to fix corrupted SD cards.
Before formatting, you should be aware that formatting will erase every piece of your images and videos, therefore, use an SD card recovery tool to restore data first. Here's how to use iBoysoft Data Recovery for Mac to recover data from corrupted SD cards.
Step 1. Free download iBoysoft Data Recovery for Mac on your device. Connect your microSD card to Mac via an SD card adapter.
Step 2. Launch this Mac data recovery program. Under Storage Device, choose your microSD card and click on Search for Lost Data.
Step 3. Preview the found files to make sure they are not corrupted. After selecting desired photos and videos, click on the Recover button.
Remember to save the found files in a new location.
After successful SD card recovery, you can now move forward to formatting the SD card on Mac by using Disk Utility.
Step 1. Open Disk Utility from Finder > Applications > Utilities. Under the View tab, click on Show All Devices.
Step 2. Select the problematic SD card from the left disk list, then click on the Erase button in the right window.
Step 3. You'll be asked to give a name and choose a format for it. Please choose exFAT or MS-DOS (FAT) here. Keep the GUID Partition Map unchanged.
Step 4. Finish the process by hitting on the Erase button. Now your SD card should work as a new one.
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