Not receiving 'Ask Permission' requests (as parent)

Hello,

I have a child set up in our 'family sharing', with 'Ask to buy' enabled on his account. When he tries to download an app, it prompts him to 'ask permission' from his parent (me), but I do not receive any notifications on my phone.

I have already read the pertinent documentation here: Set up Ask to Buy - Apple Support (https://support.apple.com/en-us/105055) including the sections titled "How to approve or decline a request" and "Can't find your Ask to Buy notifications?" and I tried those suggestions, to no avail.