Why do I have an underpayment penalty when I've made all my quarterly estimated tax payments for 2024, and when my taxes are not due for 2024 until April 15, 2025

the most likely reason is that withholding and timely estimates were less than the lesser of

1) 90% of your 2024 tax or

2) 100% of your 2023 tax (110% if your adjusted gross income was over $150,000 for 2023) 

If you get a penalty on 1040 line 38, you might be able to eliminate it or at least reduce it. You can go to Federal Taxes tab or Personal tab, under Other Tax Situations and select Start by the Underpayment Penalties. You will answer a series of questions that may reduce or eliminate the penalty. Or you can elect to have the IRS figure the penalty for you. It's form 2210.

How to add form 2210 for Underpayment Penalty
https://ttlc.intuit.com/community/tax-payments/help/how-do-i-add-form-2210/00/25703

It's under

Federal or Personal (for Home & Business Desktop)

Other Tax Situations

Additional Tax Payments

Underpayment Penalties - Click the Start or update button

There are several reasons you may owe taxes even if you paid estimated taxes during 2024 which affect your taxable income. Some common reasons are:

• New sources of income 
• Fewer deductions
• Fewer credits
• Change in filing status

Refer to TurboTax Help article Why do I owe taxes? for additional information.

@chuckohara33