When you look at your Form 1040 what credits do you see?
Look at your 2018 tax return to see the child-related /dependent credits you received:
Child tax credit line 12a
Additional Child Tax Credit line 17b (schedule 8812)
Credit for Other Dependents line 12a
Earned Income Credit (EIC) line 17a
Child and Dependent Care Credit line 12 (comes from Schedule 3 Form 2441)
The dependents you listed are on the first page of your Form 1040 below your address.
Two possible reasons:
1) You absolutely *must* indicate the child lived with you "the whole year".
2) Theres a screen that asks about support. The screen is asking if the ***CHILD*** provided more than half of "THEIR OWN" support. You probably mis-read that question and incorrectly selected YES. So under the Personal Info tab work back through the dependent child's information again and read each screen entirely, and carefully so you make the correct selections.