Here is what I have learnt.
1. It may not work with premium themes because every premium theme may have different parameters and classes assigned to post images.
2. It certainly does not work with other post types unless you modify the codes accordingly. And that is something you do at your own risk unless you are a professional coder and know what you are doing.
I suggest that you check it with changing your theme to one of the default themes provided by wordpress. Or hire a wordpress expert if you want to keep the theme and still want to apply the plugin.
Goodluck.