If neither box is checked, leave both boxes unchecked in TurboTax. This is normal. There is no requirement for one of the boxes to be checked. The two boxes are two independent questions, not an either-or choice.
You can process your return without them being checked. The line 2b shows If the distribution was a total distribution that closed out your account, and it also could be checked to indicate that your financial institution have not determined the taxable amount of the distribution. It will be determined during the tax return preparation.