SceneKit dynamic object falls through static floor

I have a SceneKit game in swift and in it I have a car with a dynamic physics body that is set up like this:

let carScene = SCNScene(named: "art.scnassets/truck.scn")!
    let carNode = carScene.rootNode.childNode(withName: "Cube", recursively: true)!



   let carPhysicsBody = SCNPhysicsBody(type: .dynamic,shape: SCNPhysicsShape(geometry: SCNBox(width: 5.343, height: 12.125, length: 4.373, chamferRadius: 0)))

    carPhysicsBody.mass = 3
    carPhysicsBody.friction = 2
    carPhysicsBody.contactTestBitMask = 1
    carNode.physicsBody = carPhysicsBody
    carNode.position = SCNVector3(x: 0, y: 0, z: 5)
    carNode.physicsBody?.applyForce(SCNVector3(x: 0, y: 50, z: 0), asImpulse: true)

    car = carNode
    floorScene.rootNode.addChildNode(car)

The floor's physics looks like this:

As you can see the car gets launched into the air. Then the gravity in the scene makes it fall, and instead of colliding with the floor, it goes right through it.

The gravity looks like this:

What should I change so it will collide with the floor?