As you might guess, you don't provide enough information for another user to help you.
Supposing TT isn't wrong, as you suggest, there are various explanations for why there might be a difference. For instance, the tax tables are not always used to calculate your tax. Other things can affect this, like if you have capital gains.
So what can you do, other than share your actual return, which isn't really feasible here since this is a public community forum. Here are some possibilities:
1) Make a single change in your tax return. Does the small change get accurately reflected by the change in your tax? Try changing different things until you find where the discrepancy originates.
2) Look for help on "Why is my tax different from the tax table?" either in TT or online generally.
3) Look for a tax computation worksheet. (I use the downloaded version rather than the online version so I'm not sure exactly what you see, but there is a worksheet that does this calculation, and usually it can either be accessed under forms or by looking for the "source" of the entry for taxes on your federal return.
4) Use a tax estimator program to get a third opinion, and see which it agrees with--your manual calculation or TT's. Here's one: https://www.mortgagecalculator.org/calcs/1040-calculator.php
Other people may have other suggestions, but hopefully this will give you some ideas where to look. IF TT is making a mistake, you can narrow down where that mistake might be, but this is something that would be carefully error-checked before it got to you :-), so it's probably not just a general error in calculation.
