Vanessa has a two-year-old 27" iMac. She uses it for her drone photography editing, but her SD card adapters aren't reading. Leo suspects that the SD cards aren't reading because of the format they've been formatted in. It may be due to formatting the card in the drone itself. Leo recommends Disc Utility on the Mac and format the card with ExFAT. Copy off the data first though with a Windows machine. Also, make sure you use a card that the Mac supports. Another way is to connect the drone to your iMac with a USB cable and see if you can get the data off by using the drone as your card reader. Check out this forum post - https://mavicpilots.com/threads/mac-cannot-read-mavic-formatted-sd-card.35785/. You may also have a failing SD card.