No App Store on Child’s iPad

I purchased my 11 yr old an iPad mini 4 and attempted to set him up as a child under family sharing account. He has a new child Apple ID and is added as a child under my family sharing on my Apple ID. When I set up his iPad his App Store icon disappeared. I reset his iPad and while the App Store icon reappeared he was no longer associated with my family share account. I reassociated him and boom. His App Store icon disappears. How are we supposed to download any content other than from the iTunes icon if there is no App Store? This renders his iPad essentially useless. Help! How do I keep him as a child on my account and allow him access to the App Store?