Why can't I add collision module to my particle in Cascade?

I’ve got a falling-brick mesh particle, and I would like the bricks to bounce a bit when they hit the ground. But for whatever reason, the collision module in Cascade is X’d out when I add it. I’m not seeing anyone else online encounter this issue. For the record, I really need this specific module, as “Actor Collision” has no bounce options.

Any answers here?