I have a ASRock Fatal1ty B450 Gaming-ITX with the latest BIOS 3.40. As I want to power it on remotely, In Bios setting I enabled ‘Restore on AC/Power Loss’ option on BIOS, but it's not working.

Then I found below and upgrade my bios firmware to 3.53, and everything works just fine! You can find the v3.53 on below link.