Books aren't showing up as "on device" when using KOReader

I recently went back to using KOReader on my Kobo, and for some reason now when I connect my device, there aren't any books showing up as "On device" in Calibre. They are there when I disconnect, but I can't tell which books are on the device and which from my library aren't.

I'm sure it's an easy fix, so can anyone help?