When I remove my kids from the tax return (they're not eligible for the Child Tax Credit) I instead owe federal $4k. Why?

Last year, the accountant we used had our children on our tax return, but did not claim the child tax credit, since they're not eligible without a SSN. Now, when I do not add them to the tax return, it says I owe federal $4k. Why is that, since we didn't get the child tax credit last year and don't want to claim it this year either, we shouldn't owe them anything as far as I understand. Can I remove the 8812 form from my tax return? Will that help?

Filing paper form so wan't to make sure I do it the right way.