how do I reactivate my child's account. He did too many wrong password attempts

If the message says your Apple ID is locked or disabled, click here and read what to do --> https://support.apple.com/HT204106 "If you or someone else enters your password, security questions, or other account information incorrectly too many times, your Apple ID automatically locks to protect your security and you can't sign in to any Apple services."

Also note "What to do after [or before] you change your Apple ID [email address] or password". Click here --> https://support.apple.com/HT204071 - "After you change your Apple ID email address or password, you might need to update your sign-in information with any Apple services you're using."

Recover your Apple ID when you can’t reset your password - "If you use two-factor authentication and can’t sign in or reset your password, you can regain access after an account recovery waiting period." - https://support.apple.com/HT204921

If you cannot resolve it yourself try one of these contact methods:

- Click here --> https://support.apple.com/choose-country-region/media-services Select your country, then a product.

- Contact Apple for help with Apple ID account security - https://support.apple.com/HT204169

- Contact Apple for support and service - "See a list of Apple phone numbers around the world." - https://support.apple.com/HT201232