You will have to amend the 2020 tax return for the Recovery Rebate Credit that you did not receive.
See this TurboTax support FAQ for amending a 2020 tax return - https://ttlc.intuit.com/community/amending/help/how-do-i-amend-my-return/00/27439
You should check your tax account to see if the IRS has sent the stimulus payment to you - https://www.irs.gov/payments/your-online-account
- Notice 1444: Shows the first Economic Impact Payment advanced for tax year 2020
If your tax account shows that it was sent but you did not receive the payment then follow the procedure to start a trace on the payment QF8 - https://www.irs.gov/newsroom/2020-recovery-rebate-credit-topic-f-finding-the-first-and-second-econom...
