Many of our clients encounter this problem: Revolution Slider plugin is not included in the theme package.
The problem often manifests itself during the required plugins installation. Users often see “Something went wrong with the plugin API” message.
This problem can be observed in all our themes that use Revolution Slider: Diamond City, Chromium, Handy, Bikeway, Brideliness, and others.
To resolve this problem you need to request the plugin by creating a ticket at https://themeszone.freshdesk.com/ (please make sure you provide your Envato purchase code in the ticket, here’s how to find your Envato purchase code!), download it, install it on your site, and then import the demo content for the slider.