Stand By mode on iPhone 13 Pro Max with iOS 17 not working

Not sure if anyone else is experiencing this but since updating to iOS 17, I cannot get standby mode to work. I have tried everything they say:

rebooting, turning it off then on again, making sure orientation lock is off. Using apple certified chargers, etc etc. still won’t work.

is there a way to reinstall 17? Or something else I should be looking at?

this is on an iPhone 13 Pro Max. In perfect condition.

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