Lightmass Portals don't seem to affect scene

I have set up a small scene inside the FPS blueprint template to experiment with some lighting setups. I wanted to give the new lightmass portals a shot since I haven’t had a chance to try them out yet. I have placed two of them in my scene, one in this large opening and one in a small window in the back left corner. After taking screenshots of the scene (production build quality) with and without the portal, I can’t seem to notice any change in the lighting. I’m not entirely sure what I am missing here, and information on this feature seems to be a bit sparse. Any help would be greatly appreciated.

Hi WolfGrizzly,
Did you build the lighting?