Thanks for asking! There were some changes for shortcodes. We’ll update documentation this week.
Instead of using [elm_randomize category=”all”], you should use [elm_random category=”all”].
And, “category” param should be the category ID and not slug. We’ll add category slug support in the next version. Do you know how to get the category ID? If not, then you can get it from category edit page. See this screenshot: http://prntscr.com/9qcs40
Please let me know if you have any more questions.