Following up on my comment to the first answer: The only way I was able to enter a 1244 stock loss was by purchasing the CD/Download version of Turbotax and going into Forms mode to add/edit Form 4797 directly. According to this answer:
https://ttlc.intuit.com/replies/7177886
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TurboTax CD/Download versions Deluxe, Premier, and Home/Business all include Form 4797."
And here's some more info on Forms mode including how to move your return from the online version to the desktop version:
https://ttlc.intuit.com/replies/4225672
Also worth noting from here: https://ttlc.intuit.com/questions/2577481-why-would-i-use-forms-mode
"It's OK to switch to Forms Mode if you want to look at a form or two, but constantly switching back and forth between Forms Mode and the interview has been known to cause problems and data corruption."
