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kathyfromboston - immediately after adding an epub, and there's no cover, what happens when you do this?
Does the expected cover appear over on the right, where you see the big brown shiny book? If it doesn't then the book has nothing that calibre recognises as a cover. You'll have to open the book in the Book Editor to figure out why that is.
If it does - then why didn't Add Books find it
FWIW there is an option in Bulk Metadata Edit to extract covers from format files
BR