Screen time not working on IMac

I have setup screen time for my child. The limits sometimes work for him, but other times it seems to not be the case. I have setup 2 hours of use for example and yesterday he used for well over that amount due to a making another instance of an app. Today, I logged in to check what he has been using and screen time show 0 usage for at least the last week - that is completely wrong. Give or take I am okay with, and me not adding an app, okay, but not showing any use when there was, I was with the child is just bad. Please help, I cannot believe this is so bad on a brand-new computer.