Thank you GeoffR.
Now I'm having
another problem! I've tried to inset a SanDisk 8GB microSD into the reader. It keeps telling me that it can't read the card and that I need to reformat it to Fat32 -- but it already is Fat32! I've tried reformatting the card but keeping it as Fat32, then I formatted it to exfat and back to fat32...
It just won't read it, and it's definitely an issue with the Kobo. The card is fine and works in everything else I've plugged it into.
The microSD card slot is one of the main reasons I bought a Kobo!