I successfully installed the Navis Slideshow plugin, and followed the directions to add a gallery. The gallery successfully displayed in the post. Since Wordpress Gallery includes in the gallery every image associated with the post, I visit the HTML tab of the Edit Post screen and added the "exclude" short code to remove a few of the images. The excluded images still display in the post.
I'm running a child theme of the Argo theme and using all of the related Argo plugins (awesome stuff!). This plugin when activated appears to conflict with the WordPress screen options โ not allowing you to make new options appear or disappear in the Menus area of the Appearance section.
I deactivated all my plugins and reactivated each one, testing to find the conflict.
Please let me know if I cab help in any way โ I'd be happy to test a solution.