iPad Air iOS 12.3 - Screen Time Control

My son’s iPad is operating under his iCloud account (in settings). I have turned on Screen Time and when prompted at the question ‘is this your iPad’, I select “no” and select the other option of being my child’s. For 3 weeks my child has been able to go over his screen time limit because when he gets the message “Time Limit Reached”, he simply selects “Ignore Limit”. There is no option for the parent to enter the screen time code (I did set one up in settings in screen time menu). I’ve also noticed the game RODBLOX has no time limit, even though I have set that limit under ‘games’. Why can’t I control my son’s screen time anymore???????