Why cant I buy individual pets????

Hi there!
I am trying to buy individual pets but it doesnt let me, it opens an other window that says; grown ups only please enter the numbers.... Why does it say that?? Please fix this thing immediately please!!!! Thank you and please try to fix it soon,, and about the game it is very fun for kids to play with their pets and they could have fun petting them and has videos for them to watch! I think this is an great game!!! But you have to fix my problem... Thank you and fix this thing fast please!!!!!

Princess of England lydia about Palace Pets in Whisker Haven, v1.2