After you file

I filed on 2/13/21.  When I did my return using your program and I got to the stimulus credit section, I filled in the amounts I received , $2400 and $1200 and your program said I qualified for a $1200 stimulus tax credit.  It's been 3 weeks with no refund yet so I ran your program again changing NOTHING and it now says I do NOT qualify for the stimulus credit and my refund is less.  Why would you make such a huge mistake like that?  How do I fix YOUR mistake with the IRS so I can get my refund?