Child Tax Credit - Infant Born in Dec 2021

When inputing info for the Child Tax Credit, I placed the info it requested for the advanced payment we received for our 3 year old - $1800 (per the IRS mailed form my wife and I received). So we received the additional $1800 remaining as a credit. We had a baby in Dec 2021. It will not allow me to claim him for the Child Tax Credit although he was born in 2021. Any tips or advice on this? Should we be receiving the full $3600 for him since we did not receive advanced payments for him? Or am I missing something. Thank you.