Is there a way to claim/file missing child tax advance payments? I did not receive 3 out of 6 checks but Turbo only gives a yes or no option, my answer is neither.

Yes, if you qualify then you will receive the remaining Child Tax Care Credit amount on line 28 of Form 1040. 

1. Click on the "Search" on the top and type "Child tax credit"
2. Click on “Jump to Child Tax Credit” 
3. Continue through the questions until the "Tell us about any advance Child Tax Credit payments" screen and enter the advance payment amount from letter 6914.
4. Continue through the questions.

Please see What is the Child Tax Credit? and IRS 2021 Child Tax Credit and Advance Child Tax Credit Payments FAQ for additional information.

To preview your Form 1040:

1. Click on "Tax Tools" in the left menu
2. Click "Tools"
3. Click "View Tax Summary" in the Tool Center window
4. Click on "Preview my 1040" on the left

If the amount shown on letter 6419 doesn't match the actual amount received then you can verify the amount on

 the IRS website.  If your number is definitely incorrect then you will need to call the number on the letter and speak with the IRS to fix it.  The number is 800-908-4184. 

Please keep in mind if you are filing married filing jointly then each spouse will get a 6419 letter with half the amount. In this case, you will have to enter both amounts into TurboTax in the Child Tax Credit section.