Thumbnails for new posts not showing up on Home Page

I just moved from Blogger to WordPress–transferred 10 years worth of posts. After many travails I finally got the blog set up using the Hueman theme. All the old posts are displaying more-or-less properly and the post thumbnails are displaying properly on the home page. Then I decided to add some new posts, but none of the new post thumbnails will display on the home page–just empty boxes where the thumbnails should be. Images display fine on the post pages. Have tried numerous times without success. Any help would be appreciated.

The page I need help with: [log in to see the link]