Child not sharing iCloud storage

I have Family sharing setup for myself and 4 family members. When I look at account storage, all of us except my youngest (who recently got her first phone) show up under family storage. On youngest's phone it shows her as part of the family but shows her storage plan as the 5GB. Share iCloud+ with your family – Apple Support (AU) says "When you share iCloud+, any family members using the free 5GB plan will be added to your family plan automatically." I'm not sure why this isn't happening and how I can recitify it.