Where do they go?

[ehani]

Hi all I'm hoping someone can help me. I download all my amazon books to my laptop, I sort and tidy using calibre then I send to my voyage. Nearly all my books show up on the screen in the order I want. However there are 2 authors whose books vanish from my screen within 30 seconds of uploading, When I look in the documents folder on the kindle these books are there but they don't appear on my screen. I've rebooted, reset the kindle to no avail.

If anyone could help I'd be grateful

Thanks