It seems that when entering the Form 1099-R that reports the distribution from the traditional IRA that you did not tell TurboTax the amount that was converted to Roth. You must indicate that you moved the funds to another retirement account, that you did a combination of rolling over, converting and cashing out, then indicate the amount converted to Roth.
(Note that if what you did instead is an in-plan Roth rollover in a 401(k), 403(b), 457(b) or the federal TSP, which are not IRAs, the taxable amount of such rollovers is not excluded from this MAGI. An in-plan Roth rollover would be reported with code G in box 7 of the Form 1099-R while the payer would use code 1, 2 or 7 for a Roth conversion from a traditional IRA.)
