There is only one 1400 per person credit for the 3rd Stimulus payment. If you didn't get it or qualify for more (like if you had a baby or added a dependent) you claim it as the Recovery Rebate Credit on 1040 line 30. It's for the same credit. You said you already got the primary credit. That was it. You only get 1. You tried to claim it again on line 30. So the IRS took it off your return.
