Just solved this problem for my friend who recently filed and forgot to request the recovery rebate credit for her child. She received $1200 for her plus $500 for her child on the first round. On the second round she received $600 but nothing for her child. This is what you can do.
1) Start new return
2) Click on "Amend a Filed Return"
3) Browse and navigate to your original return
4) Save it with a new name that includes "Amended" so you don't get confused.
5) Then click continue and answer if had filed already, In her case she had filed.
6) Click I need to amend my 2020 tax return, the amount on the top bar changes to $0
7) Click on "Federa Taxes" tab, then click on "Federal Review" button
😎Answer Yes or No, did you get a first or second stimulus
9) If "No" confirm it, if you received it but with the wrong amounts "click Yes" then, "No" and enter the amounts received.
10) It will show you the credit you should have received but the refund amount on the top didn't change right. That's where the workaround comes in.
11) Click on the "Forms" button in the blue bar.
12) Click on "1040X" on the left side menu and scroll to the box titled " Manual Selection of Lines Calculated Smart Worksheet.
13) Click the little box "E" (Lines 10-23 -- Payments and Refundable credits.
14) And Bravo! the refund amount will appear on top and you can click back on the "Step-by-Step button to finish your Amended Returns.
Good luck
