How can I receive 'Ask to Buy' notifications on my iPhone?

I control the family settings and accounts from my iPhone. I turned on Ask to Buy on my kid's iPad (after he learned he can make all the purchases he wants by resetting the password), but my iPhone never gets the notifications. Later, I can see on my MacBook that the notifications for the purchases were sent to my MacBook via the Messages app as messages from my son. But only on my Macbook. Those messages are not synced on my iPhone, I can not see them on my iPhone. I have updated all devices to lates os. I have restarted all devices. I am on home wifi. What am I missing?

[Re-Titled by Moderator]