Let's start over. You said you checked your bank accounts and didn't see the 3rd Stimulus payment that came out starting last March 2021? It might not have been for the max 2,800 if your 2020 income was too high. So look for any deposits from the IRS or Treasury.
If the IRS sent you letter 6475 (if you are married you should each get a letter 6475 for half) then the IRS records show they sent it to you. How much does the letter say?
If the IRS thinks they sent it to you then you can not claim it on line 30 again. Or the IRS will just take it off your return and send you a bill.
If the IRS thinks they sent it to you but you didn't get it last year request a trace for a missing third Stimulus payment
https://www.irs.gov/newsroom/questions-and-answers-about-the-third-economic-impact-payment-topic-j-p...
Nobody can change your return but you. Have you filed yet? But Line 30 should be 0. You can't claim 2800 on it because the IRS already sent you the 3rd Stimulus payment or thinks they did.
