Illegally claiming my dependents

Hello I'm not sure what my next step is supposed to be. I tried efiling my taxes and was denied. Someone claimed my dependents illegally. This is second year in a row that my aunt claimed my kids with no right to do so. My kids lived with her from Nov 4 2020 until Feb 13 2021. Yet she felt she had a right to claim my children when she never financially supported my kids. She got the child tax credit and the monthly payments for my children as well. What exactly do I need to send in with my taxes filing by paper?