Perhaps the first two reduced your tax liability to zero.

For the child tax credit of $2,000 per child.

The child must have been no older than 16 at the end of 2019.

The amount of child tax credit you can receive is limited by your taxable income (1040 line 11a)
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 13a on the 1040 form. Additional Child tax credit on line 18b on the 1040 form.