Hi As i see in your site other image posts showing well, so there are some privacy and restrictions for which attachment picture not available. if you check other feed plugin demo which uses application token, you will see same results.
But you can use user access token which may show these images. To generate user token go to this page
extensions.techhelpsource.com/access-token-wp , this token was for plugin version 1.0, read documentation about what to set in the FB app for generating token for version 1.0. After token generation complete, use that token in plugin settings and it should work.