This question is for the 2021 tax return. Form 8938 is to report foreign financial assets. This form has been available on the IRS website for many weeks, and does not have any modification for 2021 (tax payers specify the year in "For calendar year ....)
I am assuming that you have reached the end of guided tax preparation and are able to view your tax forms and that is how you know that form 8938 is not attached. (If that is not the case then you need to do that to be sure that the form is not there)
Since the form is not there the immediate response is - does it need to be? Here are the requirements to file form 8938. Are you sure that you need the form based on the requirements? Or did TurboTax decide you didn't need it based on your answers?
If you do need it and it's really not attaching please go back through your answers to double check the numbers that you entered.
It is a good idea to first clear your cache and cookies - which means removing all of the temporary programs that can gum up your web browser. If that doesn't work, try using a different web browser.
If that doesn't work I would recommend using the "Live Expert" help in the right upper corner to see if having someone walk you through helps.
Here is a link on how to clear your cache and cookies.
Here is a link to finding a TurboTax expert.