Thumbnails not showing

This plugin used to work fine for me, but the thumbnails no longer show. I disabled all of my plugins to see if there was a conflict, but that didn’t help. I also rolled back to the previous version, and that didn’t help. So, it seems like it’s not compatible with wordpress 3.6.1? I’m not sure when the thumbnails quit showing for me.

here’s a link to my archives page:
http://tbunkers.com/19DrJro

I’ve used firefox firebug to try to see if I needed to change something with the CSS, but that doesn’t seem to be the case. I can see the URL for the thumbnails:

element.style {
    background: url("https://www.tracibunkers.com/blog/wp-content/uploads/snazzy/4178-67b2620f1171e3871f43bd57cd9a2644-110.jpg") no-repeat scroll center center rgba(0, 0, 0, 0);
    border: medium none;

and when I hover over that code in firebug, I can see the thumbnail. So why isn’t it showing on my site?

http://wordpress.org/plugins/snazzy-archives/