We cannot see your tax return.  One guess would be that when the new tax law passed last year, employers followed a different tax withholding chart--and perhaps not enough was withheld from your pay to cover your tax liability to the state.  Compare how much you had withheld for your state for 2017 to the amount withheld for 2018.  (look in box 17 of your W-2's)  And it is also possible that tax rates increased in your state.  Of course, check all of the data that you entered, and make sure it was entered correctly.