No it is not taxed and you don't have to pay it back. What happened was that on your tax return you tried to claim it again but already got it so the IRS took it off your return. Check your 1040 line 30 for the Recovery Rebate Credit. Line 30 is only if you didn't get the full amount or qualify for more.
When you fill out Turbo Tax it starts out by giving you the full amount you qualify for. Then at the end you enter how much you already got so you don't get it again. A lot of people forgot they got the deposit last March - May. Or missed one payment and entered the wrong amount. Then when the IRS reduces their refund and they check their bank accounts they have been finding the payments.
Double check your bank statements and Check your IRS account (both accounts if married)
And you should have received a IRS letter 6475 saying how much they sent you in March 2021. If you are married you each got letter 6475 for half. You had to enter the total you got into Turbo Tax.
What tax year are you working on? The current online software is only for a 2022 return, and there is no place to enter anything about stimulus payments for 2022. There were no federal stimulus payments sent in 2022.
The federal stimulus payments were made in 2020 and in 2021. Are you working on a 2020 or 2021 return---using the CD/download?
We need to understand what you are doing before we can answer or help you.