Sphere collision doesn't work when transform is rotated

Hi folks, I have collision item I update via script created this way:

In the script attached to it is the following code:

         this.rigidbody.AddForce(new Vector3(0, -1, 0));
         this.transform.rotation = Quaternion.LookRotation(-this.rigidbody.velocity);

This works great, except the model is upside down. However, if I try to set the LookRotation to the velocity (which is corect), then the collision does not occur! Any ideas why that is?

I understand I Can simply flip the model in the program and go from there, but I'd like to know why this does not work and perhaps a way to address it?

Thanks, James