Unless a newborn is subject to a custody dispute, you should always answer “the whole year“ for how long a newborn lived with you. It may be that you prevented yourself from getting the $2000 child tax credit on your 2019 return and you may have only gotten the $500 “other dependent“ tax credit, if you did not answer “the whole year“ for 2019. You may be able to amend your 2019 return to get the extra credit you missed.
Start by printing a copy of your 2019 return and look to see which box is checked in column 4 in the list of dependents, and check to see how much of a dependent credit you received on line 13a. That may also explain why are you did not receive a stimulus payment for the child.
Here are the instructions to amend.
https://ttlc.intuit.com/community/amend-tax-return/help/how-do-i-amend-my-2019-turbotax-online-retur...
