Hello elf711,
Ask to Buy is a great feature. In addition to the steps outlined in the related article, the steps listed below can be helpful in reaching a resolution for not receiving the Ask to Buy notification on your devices. You can also find these steps, along with additional steps that can help outlined in the following article.
"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."
If Ask to Buy isn't working
If you you're unable to locate the notification or continue to have issues, you'll want to reach out to Apple next. They'll be able to investigate this issue further and continue working towards a solution. You can find their contact options via the link below.
Contact - Official Apple Support
Take care!