Ex Claimed My Daughter On Her Taxes, Violated Family Court Agreement That We Would Each Claim One Child. (illinois)

2 years ago at our last child support hearing my ex, who I have 2 kids with, agreed in court that from that point forward we would each claim one child on income taxes. She agreed to this because I pay a good amount in support, and I also help her out with things throughout the year, like school registration and school clothes. The tax agreement was added to our case, and in 2023 I claimed my daughter without issue. Now this year, 2024, she has decided that since I had another child in 2023 with a different woman, that she deserves the tax credit more than I do. She contacted me stating she was going to claim both kids this year. I reminded her that it was court agreed that I claim one child each year and she responded that it didn't matter to her. My tax return has been rejected because my dependant has already been claimed. She's admitted that she already claimed both kids this year. Do I have any recourse here at all? What are my next steps to dispute this? I have been doing research online and getting mixed opinions and advice...