Apps no blocked at end of screentime limit

Apps no longer being blocked at the end of screentime limits on my children’s phones. They don’t have my password, I have selected them properly. I have selected block at end of limit. I have tried resets on my phone and their phones. I have turned them off and turned them back on. I have deleted them and reactivated them. Last week the limits all mysteriously just disappeared. The setting on their phones don’t allow them to add or delete apps without my permission. I’m at my wits end end and my children are spending almost 4 hours a day on tictok and the like. Please help!