If the IRS changed something or if you owe back taxes or child support, the IRS does not share that information with TurboTax. The IRS will send you a letter to explain why you owe. It is also possible that the IRS discovered a mistake you made, so wait for the letter.
https://ttlc.intuit.com/community/refunds/help/what-is-a-refund-offset/00/26301
Reduced Refund https://www.irs.gov/taxtopics/tc203
NOTE: You can contact the IRS Treasury Offset Program Call Center at 1-800-304-3107 to ask if they have an offset for you on file. TurboTax would not have that information.
https://turbotax.intuit.com/tax-tips/tax-payments/who-can-garnish-an-income-tax-refund/L7cPPzDyc
TurboTax does not receive feedback from the IRS regarding money that was offset from your refund. If you owed back taxes or child support, you will receive a letter of explanation from the IRS in several weeks. The WMR site will contain a message regarding your offset. It is also possible that the IRS caught a mistake you made and reduced your refund.