Unable to spawn objects that trigger overlap events

So, short version:

I’m trying to do this tutorial:

It should create a spawner that moves cubes down the line. It’s super basic. As you can see the cubes don’t move. I’ve checked it a dozen times. The conveyors work as they push static meshes with physics turned on. The spawn should spawn them with physics turned on. But they aren’t. Any ideas?

Here are the project files:

Where am I screwing up?