There is no process used by the IRS to report this type of issue.
You will just have to file your tax return with the dependent by mail if the other party already filed with the dependent on a tax return and return was accepted by the IRS.
See this TurboTax support FAQ for how to print and mail your tax return - https://ttlc.intuit.com/turbotax-support/en-us/help-article/printers-printing/print-mail-return-turbotax-online/L5bwuqXGy_US_en_US
Within a year the IRS will contact you and other party to provide proof that the dependent could be claimed on the tax return. The loser of the investigation has to pay back any refund based on the dependent plus penalties and interest.