Economic Impact Payment - Dumbfounded!

it's not up to the IRS. IRS has to follow the US Tax Code.

Talk to your congressperson, if they'll listen to you.

They're too busy trying to pass another $1,400  payment that you won't qualify for.

If the IRS had issued stimulus payment 1 or stimulus payment 2 based upon 2018 or 2019 information, you could have received a payment for your dependent.  Since this dependent turned 17 in 2019, you will not be receiving the payment on your 2020 Federal tax return.

If you have not received one or both of your stimulus checks, you will receive your payment in the form of a Recovery Rebate Credit on line 30 of your 2020 Federal tax return when you file.

TurboTax will compare your one or two stimulus payment amounts to the computations within TurboTax.  The computations within TurboTax are based upon the information that you have entered into the tax software.  If you are due an additional amount, it will be issued as a Recovery Rebate Credit (RRC) on line 30 of the 2020 1040 tax return.

In TurboTax Online, you are prompted to input stimulus check 1 and stimulus check 2 information under Review down the left hand side of the screen.

You can access your stimulus check choices by following these steps: 

• Down the left side of the screen, click on Federal.
• Across the top of the screen, click on Other Tax Situations.
• At the screen Let’s keep going to wrap up.  Click on Let’s keep going.
• At the screen Let’s make sure you got the right stimulus amount, click Continue.
• At the screen Did you get a stimulus payment? you can update your stimulus check entries. 

See also this TurboTax Help.