Supporter - Themes thumbnails not showing

First of all, the Supporter Plugin is better than sliced bread...and I really like bread (sourdough to be specific). That being said, I can't seem to figure out why the thumbnails for the Premium Themes are not showing. The thumbnails for the regular themes are showing properly. I have been looking to see if this has been answered previously so I do apologize if it is a duplicate. This is a non-priority so there is absolutely no rush. I will continue to research and post any answer if I find one.