Since we only received half of the increased child tax credit in advance why don't I see the other half anywhere in my return?

Federal>Deductions and Credits>You and Your Family>Child Tax Credit

The IRS is sending out letter 6419 to you.  It will show the amount of advance child tax credit that you received during 2021.  Enter the information from that letter carefully.   

The remaining amount of CTC that you can receive will show up on line 28 of your 2021 Form 1040.   Then it will calculate down to the refund you see on line 35a or the tax due on line 37.

PREVIEW 1040

https://ttlc.intuit.com/questions/1901539-how-do-i-preview-my-turbotax-online-return-before-filing

Click on Tax Tools on the left side of the screen. Click on Tools. Click on View Tax Summary. Click on Preview my 1040 on the left side of the screen.

NOTE:   The CTC is indeed a “credit” that can be applied toward any tax liability that you would otherwise have to pay as “tax due”  to the IRS.

The Child Tax Credit is entered on your federal tax return Form 1040 on Line 28. It is added to your other tax payments, it is not a separate refund. Your Total taxes from Line 24 are subtracted from your Total tax payments on Line 33. If you have an overpayment then that is entered on Line 34 as your federal tax refund.

You can view your Form 1040 at any time using the online editions. Click on Tax Tools on the left side of the online program screen. Click on Tools. Click on View Tax Summary. Click on Preview my 1040 on the left side of the screen.