Deductions & credits

So I have one son I claim who was 16 at the end of 2019, turned 17 in July 2020, and during 2020 my wife and I had a son in September.  We received the full amount for the older son in both stimulus checks, but not for our newborn.  I have marked the newborn as living with us all year, per the instructions, but the recovery rebate calculated only includes payments totaling the maximum amounts for 2 adults and one child for both checks.  Why is Turbo Tax not calculating a recovery rebate for my newborn?