form 1099-R

I took a distribution from a Roth IRA in 2019.  I received a 1099-R and under box 2a, "taxable amount," it was blank.  When I entered the form into Turbo Tax it added to my "federal tax owed."  I already paid taxes on this being a Roth.  I was under the impression that this should not have added to what I owe in federal taxes.  Right or wrong?