I'm having a little problem with this plugin. The pop-up doesn't show a transparent backgound. It only displays a solid gray "wall". The rest works great. I haven't made changes to CSS. Could you help me with this issue? My website is: http://juguetesdecoleccion.com/
(The pop-up is displayed after visiting 3 pages and waiting 10 seconds.)
There's another post about this issue, it appears as "solved", but it isn't, actually.