I have an ebook (Epub) that imported all right in Calibre 5. I tried to import it in Calibre 6, and it imported OK, apart from the cover. Calibre 6 generated image file cover.jpg, and placed that in the folder with the Epub. However, the image didn't show the content of the image, but a file name.
I've checked this Epub with Sigil, and it does have a cover, one of the images in the Epub actually serves as cover, but it isn't marked as such in the Epub. That's probably why Calibre generates a new one. Calibre 5 seems to pick the correct image, and shows it correctly, but Calibre 6 just shows the name of the image. In fact, the file name is correct, so if it would display the content of the image, instead of the name of the image, Calibre would show the right cover.
I've checked this Epub with Sigil, and it does have a cover, one of the images in the Epub actually serves as cover, but it isn't marked as such in the Epub. That's probably why Calibre generates a new one. Calibre 5 seems to pick the correct image, and shows it correctly, but Calibre 6 just shows the name of the image. In fact, the file name is correct, so if it would display the content of the image, instead of the name of the image, Calibre would show the right cover.
