This makes me think there is a problem with the internal SD card. When it was connected to the Mac, did you copy any files to the drive? Another test would be to do the factory reset, connect to the PC but not start the Kobo desktop. Then see what happens if you copy a few files to the drive. If that fails, then I think it is the internal card.
In any case, I would probably return it and get a replacement. If for some reason you can't do that, you can open it, take the SD card out and test it. Or replace it with another. You will need an image to do that, but that can be supplied.
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