@mayz21lb-
First stop focusing on the first possible reason on the generic list they sent on that notice ... it is only the last one ... the stimulus credit you took on your return that they are focusing on ... look on the form 1040 line 30.
Now did you say you got the missing stimulus money AFTER you filed with the credit on the return ??? If so the IRS is saying you cannot have the credit at all ... you don't get the stimulus payment AND the credit. So they removed the credit from your return and now you don't have a refund you have a balance due. Review your return ... remove the credit on line 30 and recalculate the rest of the return ... is the IRS correct ?
