Hey Boris, nice to see you are still with us
The collision tests are 2d-only at the moment. You can still make it
work by adding a Condition-component to the OnCollision property list
which tests the z-value.
You also need to take care that you won't have repeated collisions.
When you reverse the z-velocity, it will immediately collide again
and reverse once more

. I added a line to move the ball just outside
the collision test in the z-axis when colliding.
Btw, I like the shadow
See attachment.