This isn’t interesting unless you happen on it because you’re having the same problem.
I’d been using JetPack’s Carousel feature for WordPress for quite a while, and liked it. I noticed recently that it had stopped working. Still enabled, and looked as if it should be working, but not happening – images were just taking me to their image page. I’d forgotten that I’d enabled W3 Total Cache’s Minify feature – it minifies JavaScript, among other things, and it looks like it breaks Carousel. Turned it off again, and Carousel started working again.