If the child is age 17 or older in 2020 they are not eligible for the child tax credit.
If the child is under the age of 17, then you need to verify your answers you entered for them as a dependent in the My Info section of the program.
Verify their date of birth, that you selected they were your Child, that they lived in your home for the whole year, that the did NOT provide over one-half of their own support, that there was not another person in the household supporting them. That you were the parent who could claim the child as a dependent. That they have a valid social security number.
If everything is correct and you are not getting the CTC, delete them as a dependent and then re-enter.
The interview should tell you the reason.
For the child tax credit of $2,000 per child.
The child must have been no older than 16 at the end of 2020.
The amount of child tax credit you can receive is limited by your taxable income (1040 line 15)
If your taxable income is zero, then you are not eligible for any child tax credit.
However, if you do not qualify for the Child Tax Credit, and if your earned income is greater than $2,500, you might be eligible for the Additional Child Tax credit. That amount is 15% of earned income greater then $2,500 up to a maximum of $1,400.
Too high of an income will reduce or eliminate the CTC also.
Married Filing Joint - $400,000
Single, Head of Household, or Married Filing Separate-- $200,000
The child tax credit will be reported on lone 19 on the 1040 form. Additional Child tax credit on line 28 on the 1040 form.