This indicates that the payer lost track of your investment in the contract. TurboTax used to properly ask if under these circumstances the amount in box 2a represents the correct taxable amount and, if not, allow you to indicate that you used the General Rule to determine the taxable amount and allow you to enter that amount. TurboTax would then simply place your entered taxable amount in box 2a of the Form 1099-R. Beginning with 2024 TurboTax, this necessary question was removed from TurboTax, so you'll need to enter the $0 taxable amount in this case in box 2a yourself.
In case the IRS questions your indication that $0 is the taxable amount, be sure to retain whatever records you have showing your investment in the contract that justify your assertion that the taxable amount is zero.
