I was not prompted by the program to enter income from a retirement fund in 2021. The amount was not entered. Is this something Turbotax can be held accountable for?

If you did not enter all of your income for 2021, then you will need to amend your 2021 return.   If you go systematically through the Wages & Income section of the software, you have screens on which to enter retirement income.  It seems that you missed that or forgot to enter your retirement income.    TurboTax provides do-it-yourself software---it is up to you to check and make sure you have entered all of your income.

See this TurboTax support FAQ for amending a tax return - https://ttlc.intuit.com/turbotax-support/en-us/help-article/tax-return/amend-change-correct-return-a...

To enter your retirement income, Go to  Federal> Wages and Income>Retirement Plans and Social Security>IRA  401 k) Pension Plan Withdrawals to enter your 1099R.

You are responsible for entering all your income.  Using the guided interview, if you go through all the steps and don't skip around, you are asked about 1099-R income.  If you don't use the guided interview and click "let me choose what to work on", it is your responsibility to make sure all your income is entered.  

If you are being assessed taxes and interest on unreported income, and you agree with the amount, just pay it. You do not need to file an amended return.  If you think you don't owe tax or that you owe a lesser amount than the proposed assessment, you can prepare an amended return to show the lesser amount.  However, don't file the amended return using the usual instructions.  Instead, mail it to the office that sent the assessment.