iframe won't work with theme, but works as a plugin

Hi Guys

I use a theme called Plexus for my multipage blognetwork. It works fine for me, but I can't get an iframe to work on this one page I have:
I tried to get it to work on this page, but for some reason it doesn't work.

When I insert it as a widget on one of my other pages it works fine, so not sure what to do here. It works on this page, on the right side widget in the bottom: http://kasperstent.dk/2017/06/03/europaeisk-succes-hjemlig-fiasko/