Mesh Highlight not shown on camera view

I created a post process material to highlight meshes when I select them. I can see the highlighted on the player camera’s view. I have a different camera actor and have it’s view rendered on a widget’s image as a material. In this view, I can’t see any highlighting at all.
I’m not sure where things are going wrong (is it the actor, widget, image or material that’s messing things up?).