Received a CP11 notice from IRS saying I miscalculated my Recovery Rebate Credit

I received a CP11 saying that I calculated my tax wrong and that I owe an additional $898, which is EXACTLY the amount calculated by TurboTax on the Recovery Rebate Credit Worksheet.  Essentially, the IRS notice seems to be saying that I'm not entitled to that credit.  I have reread that worksheet and all related IRS material about a hundred times now, and as I see it, we (married filing jointly with an AGI below 150K) should be entitled to $2800, but back in March 2021, we received $1902.  Therefore, the credit on line 30 should be the $898 that I filed.  I am unable to get through to the number provided in the letter.  I also contacted TurboTax, but unlike in prior years, where someone was able to advise me on it, I am being told that I need to talk to the IRS or a CPA. I am convinced that my and TurboTax's calculations are correct.  Can anyone think of a reason that the IRS might be correct instead?