Just to be clear, you are talking about the vanilla Page Preview (core plugin) and not the Hover Editor community plugin, right? (I don’t see Hover Editor in your plugin list, but just wanted to be sure.)
I’d try in the Sandbox vault first. Does the Page Preview pop-up work as expected there?
Then you can move onto your vault. Is the plugin enabled? Try in Restricted mode, no CSS snippets, and using the default theme to see if it works then. All the troubleshooting steps are here.