Spawned actor can't be overlapped?

After increase the z extend of the box collision component, this poroblem got solved.

I have a blueprint actor: MapBlock with a PlaneComponent as its root component, with a BoxCollisionComponent attaches to the plane, everything seams to right, I tragged one MapBlock into my scene and tested it, my player overlapped with it.
Then I use spawnActorFromClass to spawn my MapBlock one next to another, no overlap events was triggered, I have no idea about this, please tell me why, thank you so much!