Even though I included two 1099-NEC forms, TurboTax did not include the self-employment tax on our return and now we owe the IRS with interest. Am I missing something?

Where did they show up on your return?  You needed to fill out Schedule C for them.   Did you know they were for self employment income?  Do you have any expenses for it?   You can enter Self Employment Income into Online Deluxe or Premier but if you have any expenses you will have to upgrade to the Self Employed version or use any of the Desktop CD/Download programs.

Is the income from 1099-NEC forms included in the gross business income on line 1 of Schedule C? If not, or if there is no Schedule C in your tax return at all, you may have entered the 1099-NEC forms incorrectly, or you may have answered a question in such a way that TurboTax did not treat them as self-employment income. After you enter a 1099-NEC TurboTax asks whether certain "uncommon situations" apply. Did you select one of the uncommon situations? Or you may have entered the 1099-NEC but did not complete the business income section.