Recovery Rebate Credit Rejected By IRS

I did not receive either of the stimulus checks during 2020 even though I more than qualified for them.  When I filed my 2020 return on TurboTax I was prompted through the Recovery Rebate Credit section by TurboTax and received an $1,800 credit approved by TurboTax.  That Recovery Rebate Credit brought me from owing $500 to receiving a $1,300 refund.  Several weeks ago I received a letter from the IRS rejecting the Recovery Rebate Credit without any explanation and demanding a $500 payment.  How can that be?  I didn't receive either stimulus check in 2020 and TurboTax guided me through the Recovery Rebate Credit on my return and approved my return for submission.  I replied to the IRS letter with a letter explaining the above which got nowhere, but I wanted to have a paper trail.   a second IRS letter was just received demanding payment in a week.  Does TurboTax  back up returns that they have approved and the IRS disapproves?  There's no online support when you go to there site like there is during tax season.  It seems totally unfair to not receive either stimulus check  and then get rejected by the IRS for the Recovery Rebate Credit.  Is there any way I can get some justice with this issue?