Screen Time on iPhone won't work after getting deleted using third-party app

My son used a third party app (Nugget) to remove screen time control and now I cannot find a way to set it back again.

Even when we go to Factory reset or install a new OS version and then log in to his account and download his data from cloud, the screen time is still not working. Possibly the setting is kept through his cloud recovery save, but I don’t know how to get over this problem? Thank you.

[Re-Titled by Moderator]