Changing AO parameters

Greeting

There is video about ambient occlusion (https://www.youtube.com/watch?v=zvJg1-hLKYs&t=2s)

Trying to reproduce it, I didn’t get anything right at the start.
When i try to change AO parameters then nothing changes - why?

Look at my short video

https://www.youtube.com/watch?v=qmdKIh2F8sU