Fill this out with these 6 numbers and it may help you:

--------

------------------------------------2018------------------2019
taxable income................________............_________
taxes owed......................________............_________
taxes paid........................________............_________

You will find that:
The tax that you owed was about the same. 2018 will probably be ~$400 more owed than 2019 due to your salary.
Then you will see than in 2019 the "taxes paid" was ~$1800 less than you paid in 2018.

In other words you did not pay enough in 2019

OR you stopped paying into you 401k and in 2019 you had higher taxable income.

Now it is 2020: Be sure that they are taking out enough tax in your pay check, or set aside ~$2000 to pay taxes next year.