It sounds like you are the non-custodial parent who did not get anything.
As far as the IRS is concerned, the custodial parent is the one who can claim the children. If you are the non-custodial parent and there is a signed Form 8332 you can claim the children in order to receive the child tax credit. The custodial parent still gets to file as Head of Household and may get the earned income credit and childcare credit.
If you think you should have been able to claim the children, you have to print, sign and mail your own tax return (or amended return) that claimed the children and let the IRS sort it out. If you are not the custodial parent your chances of prevailing are not good. The IRS cares about who the children lived with--not court orders.
**Disclaimer: Every effort has been made to offer the most correct information possible. The poster disclaims any legal responsibility for the accuracy of the information that is contained in this post.**