Yikes- classic "false hitch" scenario. That's how I learned to always lift up with the tongue jack just a bit after hitching to make sure it's actually hitched. Isn't it weird that you can actually close the coupler latch without engaging the ball?
Anyway, per your question:
I don't quite understand it and can't see the picture. Are you saying that you're trying to connect two parts, each of which has a closed loop?
If that's the case, could you be missing an intermediate coupling of some kind?