[Plugin: Shadowbox JS] Black box when opening .pdf?

I’m using the shadoxbox plugin on several sites, and up until the last update, it worked just fine. But with this last update, my .pdf’s no longer open. I literally changed nothing in the links, just updated Shadowbox JS. The .pdf’s used to open only when I use the rel=”shadoxbox” in the link. But now, when I hover over the link, I can see that the link to the .pdf is there, but when I click, only a black box pulls up. However, if I open it in a new tab, the .pdf still opens without Shadowbox.

What’s going on? How can I fix it?