I think I find solution. It's happen because MIUI have 2 settings app with 2 different power saver. My method to access another settings is

1. Download Shortcut Maker By Rushikesh Kamewar: Google Play

Ya It worked. Thank you ^^

My detailed activity:-

Downloaded said app

Battery saver shortcut

Clicked on "Try now"

battery saver was on - Disabled and all is fine now