TurboTax does not receive copies of letters sent to you by the IRS so no one at TT knows why the IRS changed your return or why you now owe money. Lots of people made mistakes with the recovery rebate credit that put an amount on line 30 of your Form 1040. Did you have an amount there? Did you already receive the EIP payments before you filed?
If you are having trouble understanding the letter from the IRS
TurboTax has a special phone number for help with IRS/state tax letters, which will be easier than going through regular Customer Support. At the page below, click on the blue button that says "Get Help from TurboTax Support". Then it will ask you what tax year is your letter. Then it will ask you what the letter concerns. Then it will show you the phone number during posted business hours.
Read the notice carefully ... what did they change ? Did you have an amount on line 30 of the form 1040? If so did the IRS disagree with the amount on that line by saying you already got the stimulus money in advance.