[chaley]

Originally Posted by kovidgoyal

Look at that log its full of permission errors on the thumbnail cache directory. Fix those permissions or delete that directory and it will be re-created hopefully without permission problems. See https://manual.calibre-ebook.com/faq...n-denied-error

That is a subdirectory of the directory I said you should delete in post #4 (caches). Assuming you actually deleted the directory then I suspect you have some kind of inherited permissions that prevent calibre from creating files in its own cache.