iPod won't sign in to iMessage

We just bought 2 brand new, 7th gen. iPods for our preteens for christmas. We made them gmail accounts for them and created apple ID's using those emails. Neither of their iPods will sign in to imessage of facetime. SO FRUSTRATING!! however, they WILL sign in to imessage if i use my apple ID. So that rules out any time zone errors, or a physical issue with the ipods. We have tried making different emails/apple IDs and changed their birthdates incase it was bc of their ages. Still wont sign in with ANY new apple ID we have tried to create. PLEASE HELP!!!!