The SD card is formatted with multiple partitions, and with various file systems. A Windows PC can not mount it reporting the card as corrupted. I have no idea about how MacOS handles this type of SD card.
I'd suggest getting a new SD card first, then request an image in the
Kobo µSD Card Image Requests thread and following the supplied instructions, write it to the card.
This will at least show whether or not your device is working.