If you imported your W-2, you can open your return and review what is entered in Box 12 as 401K contributions. You are correct that if 50 or older, you can contribute $23,000 plus $7500 in catch up contributions, for a total of $30,500.
Make sure your age is correct in the Personal Info section.
Why do you think TurboTax rejected your catch-up contribution? If you can give more details, we'll try to help.