Hi Kerrylou5,
Welcome to Apple Support Communities. We understand that you're having an issue with receiving Ask to Buy notifications. We'd like to help.
From what you've shared, it sounds like this resource will have the best steps to help you out with this: If Ask to Buy isn't working - Apple Support
Depending on which device you're expecting those alerts on, it would be good to start with these steps:
If your Ask to Buy requests are missing
If you miss an Ask to Buy notification, you can find the request in Notification Center on your iPhone, iPad, iPod touch, or Mac. If you still don't see your Ask to Buy requests, check your Family Sharing settings, check which Apple ID you're signed in with, and make sure that you're on a supported device.
Open Notification Center on your iPhone, iPad, or iPod touch
* From the Lock Screen, swipe up from the middle of the screen.
* From any other screen, swipe down from the center of the top of your screen.
Open Notification Center on your Mac
Click the date in the upper right corner of your screen or swipe left with two fingers from the right edge of your trackpad. Notifications show up at the top of Notification Center.
Hope that helps.
Cheers.