I am having the same issue. My thumbnail options all of a sudden dropped from 15 to 3 on FB recently, and this has happened before, ... but they don't seem to be coming back at all.
So, I installed you plugin, but am not having any luck getting new thumbnail options.
The site is http://www.crossfit-competitions.com, and the other plugins I am using are:
All-In-One SEO Pack
Fast Secure Contact Form
Featured Content Gallery
Google Analytics for WordPress
Related Posts via Categories
Taxonomy Dropdown Widget
Any help you could give, I would appreciate, as I'm tired of using the same three (3) thumbnails that are provided to me, hah.