Link to the gif->
My unity3d version is 2018.2.15f1 , The collider on the sphere is sphere collider and on the cube is the box collider, physics setting are default.
Physics material settings (ball and side cubes) -
Dyn. friction 0.05
static friction 0
bounciness 1
friction combine - average
bounce combine - average
Floor Physics material -
Dyn. friction 0.4
static friction 0.4
bounciness 0
friction combine - average
bounce combine - minimum
Your floor has set its bounce combine to “minimum”. As you can read in the docs here if two materials with different combine methods collide, the one with the highest priority is used. Minimum has a higher priority than Average, so Minimum is used. Since your floor has a bounciness of 0 the collision will result in 0 bounce which is exactly what happens.
Why did you actually set the floor bounce combine to minimum? The combination of the combine mode minimum and bounce value of 0 will actually remove all bounciness from all objects except those with have Maximum as combine mode.
edit
I just read that you seem to have the same material on the side cubes as well as on your ball (the way you posted the information is really hard to read). In this case if both have a bounciness of 1 and a combine mode of average, you just move below the bounce threshold which specifies the velocity at which no bounce will occure anymore. This threshold is there to stabilize systems with many rigidbodies which are constantly pushing each other. If it’s not an issue for your application you can lower that threshold.