we can't see your return. usually, it's because of the lower rates for capital gains and qualified dividends or even the QBI deduction on line 13 but this apparently is not your case. so after checking again that you used the correct line and column in the tax rate schedules based on your filing status on page 1 and coming to the same conclusion contact support who can look at your return
5am-5pm Pacific Time (8-8 Eastern) Monday - Friday
https://support.turbotax.intuit.com/contact
800-446-8848
