Go back through the IA return. There is probably a zero stuck in the interview. As a last resort, you can file your extension at our Easy Extension website
The instructions for Schedule 1 - Line 18 says:
Federal deductibility has been completely phased out for tax year 2024. No amounts of federal withholding, estimated payments, or payments for prior years should be deducted on the Iowa return, even if the amount paid was made towards a tax year in which federal taxes for prior years were previously deductible (2023 and prior). Federal income tax refunds or overpayments received in tax years 2024 and later do not need to be reported on the Iowa return.
If you entered these, you should delete them.
How to delete forms in TurboTax Online
How to delete forms in TurboTax Desktop
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