childs birthday in setting up apple ID

If you are following the steps in the article below and still have the problem, contact Apple ID Support for assistance.

Family Sharing and Apple ID for your child

See the Apple Support articles below for contact information.  

Apple ID - Official Apple Support.    

Contact Apple for help with Apple ID account security - Apple Support.   (Link doesn’t always load)  

Get Support          Work through the screens to get a chat option. You may have to pick a slightly different problem.

Apple Support schedule phone call

If necessary, try Twitter

https://twitter.com/AppleSupport.          

From the Apple Support article below. 

Hey i had the same problem, but i made the apple id account on the apple website instead of settings and it worked. All you gotta do after that is log in with your new apple id :)