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.
The Recovery Rebate Credit is calculated based on your 2020 income, whereas the stimulus payments were based your 2019 tax return or last return filed. If a taxpayers' situation changes in 2020, they could get a partial or the full stimulus payments based on their 2020 income.
