How to make motion blur working

Hey everyone!

I am staring to study Post Processing Package in Unity in order to use Motion blur effect in project: a simple scene where an object moves along the z-axis at a constant speed, and the main camera follows the object, environment was made from Terrain. But motion blur doesn't work in this scene. I have followed the steps below: 1) Download Post Processing Package; 2) Create Post-Processing Profile (named Effect); 3) Create a Layer "Effect"; 4) Attach Post-Processing Layer Component to the main camera (the main camera has a parent "Holder"); 5) Attach Post-Processing Volume Component and Box Collider (as trigger) to a empty gameobject (has the same parent as the main camera); 6) Assign Layer "Effect" to the empty gameobject; 7) Add Effect Motion Blur and turn it on. But motion blur doesn't work. Also I tried to attach Post-Processing Volume Component to the main-camera (with checked "Is global") (without box collider), but that didn't fix the situation. Another Post Processing effects are working (such as Bloom, Grain and etc)

Are there any ideas why motion blur doesn't work?

Thanks for the help!