Do you mean you received a notice from the IRS or from your state? TurboTax gets no information from the IRS or state after you file your tax return, so no one at TT knows why they are saying that you owe. Perhaps you made a mistake when you entered your income amounts or the amounts of tax withheld, or forgot to enter some income that the IRS or state knows you received.
I RECEIVED A LETTER FROM THE IRS/STATE
TurboTax does not receive any information from the IRS or your state after your return was filed, so no one at TurboTax knows about a letter you received from the IRS or the state.
The notice that you received tells you what the IRS or the state thinks was wrong in your tax return. What does it say? Read the entire notice carefully. They might have found more than one error.
If the notice is from the IRS there is a notice number or letter number, starting with CP or LTR, at the top right. What is the number?