Aha, Ok i see now. So the 'PlayerBox' is the object actually affected by collisions...etc... and the 'Player' is actually the 'VISUAL' of what happens to the PlayerBox?
Both are affected by collisions.
The reason it didn't work before was because the spikes have the "solid" behavior: https://www.scirra.com/manual/104/solid
And the solid behavior was reacting to the Platform behavior from the PlayerBox object, so the collision with the player object wasn't activating properly. It would also have worked if in the editor you changed the Player position 1 pixel below the PlayerBox. That way, the player object would have collided with the spikes first, but since both objects are on the same Y position, it wasn't working properly.