No one here can see your tax return to answer your question with certainty. However, my recommendation is that you go through the HSA section of your return again to verify the answers. If something was not answered correctly to determine that you are eligible to make a contribution to your HSA, then the penalty would be generated.
Pay close attention to the messages on every screen because TurboTax will let you know at what point there is a problem, and there will be suggestions offered to fix the situation.
Also, consider whether you entered any distributions reported on a Form 1099-R because these may also cause penalties that would be reported on the same form (Form 5329).