You may need to amend your return to get the amount to show up on line 28. That's the only way to get the other half of Child Tax Credit. How many children do you have and their ages on Dec 31? When you filled out your return did you enter the advance amount you already got and from letter 6419? It is possible you may not qualify for the other half, like if you made too much income or didn't claim the same number of children as on your 2020 return.
