Why amending tax return with missing spouse Roth IRA contribution of $8000 for a total of $16,000 joint return doesn't affect federal refund with income of $81,000?

I submitted 2024 joint return with only one 2024 IRA contribution of $8000. I should have also added an $8000 contribution from my spouse. I followed the TurboTax Amend Return process, adding the $8000, but the federal taxable income did not lower from $81,000.