Hi,
I built a website with Crocoblock last week, and had a problem having the featured image display on the custom post type. I changed themes (from Xstore to Kava), and the featured image returned in the post type.
I am now facing the same thing on another site, but when using Custom Post Type UI (plugin). Featured image is specified to appear when adding a new post, but the option to add a featured image is not showing.
This leads me to believe that there is a conflict between your theme and specifying a featured image in custom post types.
Everything was fine until the latest update. The CPT UI’s all worked before then.