Why doesn't TurboTax reduce cost basis for 1099-R early distribution of Roth IRA?

In 2020 I took an early distribution of my Roth IRA (I'm not 59 1/2).  The initial investment I contributed isn't included on my 1099-R form since I had rolled over the funds from my 401K into the brokerage account.  I have tried to manually enter the amount of my contributions but TurboTax isn't calculating the difference and lowering my actual taxable income.  When I enter my contributions nothing happens.  No numbers change.  I even tried inputting the amount into different lines (lines 5 and 9a).  Why is this happening?