I'm testing the plugin and it works. But there's a behavior that makes my life harder...
I use Optimize Press 2. And I'm using elements of that plugin to construct the popup - the result is awesome, by the way, and other plugins don't allow that freedom.
But the problem is that on the preview it don't use the OP2 css, so I don't see the real result. To see it I need to activate the popup, access a page that triggers it, and see the result.
The final result uses the OP2 css. The problem is specific on the preview.