First, confirm that TurboTax is treating it as taxable by seeing that it is being included on Form 1040 line 4d. If it's appearing there:
What is the code in box 7 of the Form 1099-R provided by the payer?
Does the Form 1099-R show a nonzero taxable amount in box 2a?
Does the word ROLLOVER appear next to line 4d of Form 1040?
