My experience with ZotPress is that when I'm trying to add a group and display it, the admin screen errors out unless I alter zotpress.rss.php and zotpress.default.php to not send a public key, collection name, tag name, or limit--- and even then, the shortcode doesn't work (because I didn't hack around with the javascript code as well.)
I'd be happy to provide further information via email. The Zotero public collection I'm trying to display is here:
https://www.zotero.org/groups/united_states_childrens_bureau_history (it's id 38622.)