The “show preview” function in wordpress isn’t working correctly on my sites that use the Nirvana theme (though the ones that use Tempera do work). When I make edits to published pages and hit “show preview” none of the edits are displayed, even if I refresh the page – it shows the page as previously published. However if I hit “publish”, the edits are published. Both the theme and WordPress are up to date. How can I make the preview display edits?