Autoblog is not fetching the featured image

Autoblog is processing the feed but not fetching the featured images. I have selected “Use media:thumbnail tag of a feed item”. But the Featured images are not fetching. The images in the contents are fetched.

The only difference in them is the content images urls were in https and the featured images were in http protocol. I have changed the featured image urls to https in the feed but still the featured images are not fetched.