I am using Calibre 6.17 and converting books fro EPUB to MOBI for upload to a Kindle Oasis 10th Gen. I have been doing this for years but recently couldn't find a book I was certain I had uploaded. After a quick search I discovered about 30 items that were classified as 'documents' rather than 'books'. I have looked at the metadata but cannot see any reason why these books should be different. It serious problem but rather annoying.
Can anyone advise please
Can anyone advise please