Is there another reason why I'm not getting the FULLY refundable 2nd half of the child tax credit in my refund? Children are 13, 9, 7, and 5 We meet ages

We meet the children's ages requirements, income, and all other requirements. I input the advanced credits. I see the $6300 credit (which is the other half not yet paid) under 2021 CTC and yet Turbotax refund estimate is not giving the fully refundable amount - not even close. What other reasons could be causing this?