I installed “Page Builder by SiteOrigin” plugin. I don’t see “Live Editor” menu item at the top admin menu bar even as admin. Show me a screenshot where it should be. Or do you write about “Live Editor” button located at the general toolbar together with “Add widget”, “Add row”, “Layouts” buttons?

Look at a browser JavaScript console also. Are there any error messages before and after click “Live Editor” button at top admin menu bar?