It is really based on your 2020 income. If you do not qualify for the Recovery Rebate Credit because of your 2020 tax situation then you will not be able to get the missed stimulus payment.
Per the IRS, your Recovery Rebate Credit amount will be phased out if your adjusted gross income for 2020 exceeds $150,000 if you are married filing a joint return or filing as a qualifying widow or widower, $112,500 if you are using the head of household filing status, or $75,000 if you are using any other filing status.
Did you check 1040 line 30 to see if you qualify for any more? You might have received too much based on your 2019 income so don't qualify now based on 2020. Are all 3 children showing as dependents on 2020?
