1099-R distribution mysteriously treated as nontaxable income

Hello TurboTax community! I carefully entered information from a 2023 Form 1099-R into TurboTax Premier, and TurboTax is treating it as non-taxable income. So, TurboTax says I'm getting a huge refund ... which doesn't sound right.  Is something wrong with the software or with my 1099-R?  Details: This is one of my traditional IRA accounts, it's unmanaged, it's all cash (likely came from a direct rollover of my lump sum pension when I retired three years ago), and it's not inherited. On the 1099-R, boxes 1 and 2a have the same six-figure amount. Box 2b is checked (taxable amount not determined). Box 3, box 5, and box 6 are blank. Box 7 is 7 (normal distribution), and the IRA/SEP/SIMPLE box is checked. A lot of money was withheld in box 4 (Federal) and box 14 (my state). I don't have either a W-2 or earned income for 2023. Thanks for your help!