First:
To receive any benefit from the child tax credit, you must:
1. claim the child as a qualifying child dependent, and
2a. have enough income that you owe tax, or
2b. have at least some income earned from working (unemployment, investments, gambling, and other forms of income don't count)
So now we need to know,
Can you claim the child as a dependent? If this is your legal child (adopted, step or biological), the most important test is generally, did the child live with you in your home for more than half the year (6 months and one day, or more, 183 or more days). This is not a question of court ordered or legal custody, it is a question of where the child actually physically lived. If less than half the year, there are some other ways you might be able to claim the child, but they would only be eligible for a $500 credit, not the up to $2000 credit.
There are some other factors that get involved, but the main questions will be do you have income earned from working, and did the child live with you more than half the year.
