The other day, I added a new EPUB into my library, originally downloaded from Archive Of Our Own, with some edits made in Sigil because I'm finicky about formatting. This is a standard workflow for me, and usually it leads to Calibre generating a cover based on the book's first page of text.
This time, though, instead of that, Calibre gave the book the Default Unmarked Blue Cover. When I went into the book's metadata and directly told Calibre to set the book cover from the EPUB format (the only format available), it then gave me this error:
Code:
calibre, version 4.19.0
ERROR: Could not read cover: Could not read cover from epub format
...and apparently this error has never before been posted on the Google-accessible internet, because when I did a search for the error in quotes, zero results came up. (Results when searching without quotes were existent but not actually about this particular error.)
Since then, I've confirmed that it's not a more general problem with my Calibre installation; a second EPUB I subsequently put together in Sigil got the usual autogenerated preview as its cover image, as did a third EPUB downloaded off of Archive Of Our Own and edited in Sigil in the same manner as the error-prone one. (Which continues to yield the same error, when I try to generate a cover from the EPUB.) I am, at this point, Confused.
So, my question: does anyone have any idea what might be causing that error, or how I might be able to fix it? For the moment I've fallen back on Calibre's "Generate cover" option, since it's a lot better than the Default Blank Blue Cover; but it's aesthetically off-pattern compared with the rest of my library, and as such I'd still rather find a way to make it do the usual cover-as-book-preview thing if possible.