Thank you.
Actually I have imported quite all the posts from blogspot and found the first images automatically inserted in homepage. So when I occasionally did a new post I did not understand why some images appear in homepage and others not (and I still do not understand how could it happen as I do not remember selecting any featured images).
After I posted the question I have discovered the featured image option (and signed the forum request resolved, unfortunately one can not delete it) and so I inserted manually the missing images (that’s why you have found it already fixed)
