Can't import 3D Warehouse objects

I’m having trouble importing objects from the 3D Warehouse into my model on my Mac. I can download them, but when I click to insert them into the model, nothing happens. Each model is showing up in my components window, but I am unable to copy/paste them from there. I have also tried copy/pasting my entire model into a new .skp file, but the problem still happens.

SU menu: File >> Import my be a better…