I can't change the screen lock setting

[Android Central Question]

I own a galaxy note 8. I used to have my lock as swipe and i decided to change it to iris or pin. I have an iris already registered btw. so when i went into the screen setting, and i clicked the screen lock type, what it shows me is 1 second of the iris recognition (during this time there is no actual camera of my eyes and a white screen with backup password at the bottom. i see the red light for 0.5 seconds in the iris recognition). what it does after is it wont make me go change my lock screen type but just goes back. i then tried to press the backup password and my phone opens up a tab to enter my passowrd for 1 sec and it dissapeara again. please help me.