Category doesn't work?

Hi, it seems like the categories aren’t’ working properly. If I add a category to the shortcode the images don’t show on the page. I noticed if there is not category in the shortcode the images show no problem. However, this is a problem for me because I’m using 2 different instances of the hover and I need to display them on the page. What I’m doing wrong? Thanks!

https://wordpress.org/plugins/royal-image-hover-effects/