featured_image doesn't show up, gallery images are fine

Same problem here – gallery images work, featured do not.

It seems there is a buggy line in the include/class-woocsv-product.php file.
The line #248 which contains the following code:

$imageID = $this->saveImageWithUrl($this->featuredImage);

must be removed in order for the featured image to work by name.
This line overrides the previous conditionals, and thus breaks the code.
Looking at the odd indentation, it looks as if it has been copied-pasted there by mistake.

( This line is found in the saveFeaturedImage() method. )

Hope this helps someone, until 1.2.8 comes out.

Good find Kostasx ?? Seems indeed to be a leftover of copy-paste.

Thanks @kostasx.