That was a known glitch.. TurboTax put out a FAQ with a statement that they would stand by any penalties and interest if the IRS does charge a late payment penalty. I hope they are informing the IRS about what happened, and that the IRS will take this into consideration.
In any case, see the response from a TurboTax employee in the thread below. Expand the FAQ there by clicking on the gray button "See Entire Answer", then read what it says about any penalties and the TurboTax Accuracy Guarantee.
https://ttlc.intuit.com/questions/4765546-e-file-is-telling-me-that-i-have-to-set-my-payment-date-fo...
