Those are just generic reasons why they adjusted the Recovery Rebate Credit on your return. A common adjustment is if you claimed the Recovery Rebate Credit on 1040 line 30 when you already got the 3rd Stimulus payment or reported the wrong amounts. Do you have an amount on line 30? The IRS knows they already sent it to you. Line 30 is only if you didn't get the full amount or qualify for more. Did you get letter 6475 telling you how much they sent you? Each spouse gets a letter for half. So you may have only entered half the amount instead of the total you received.
How much is missing? Check 1040 line 30. A common reason this year is if you tried to claim the Recovery Rebate Credit (for the 3rd Stimulus 1,400 per person) when the IRS already sent it to you. Line 30 is only if you didn't get the full amount or qualify for more. Not the amount you already got.
They sent the 3rd Stimulus payment (1400 per person) starting in March 2021. Double check your bank statements and check your IRS account (both accounts if married) to see what they sent you.
https://www.irs.gov/payments/your-online-account
