Hi DeeSav13,
Thanks for posting in Apple Support Communities.
We understand Ask to Buy isn't working and you were able to review If Ask to Buy isn't working - Apple Support. If you're not receiving the notifications, have the child try requesting from various apps to determine whether this is specific to an app. Make sure the child's device, as well as your device, is running the latest iOS update for the most recent performance fixes.
If this continues, contact Apple Support to check into this behavior.
Contact - Official Apple Support
Regards.