A common adjustment is if you claimed the Recovery rebate credit on 1040 line 30 when you already got the Stimulus payment or got the second one after you filed or reported the wrong amounts. Do you have an amount on line 30?
Did you already get the full first and second Stimulus payments? You had to enter the right amounts you got in the right 2 boxes. If you entered the total for both in one box then it would give you the other round again.
