TurboTax is not populating my capital loss carryover from prior years. I did not file a schedule d in 2019, but I still have significant capital losses to carry over?

You can enter it manually.

Just open your TurboTax return, search for capital loss carryover, and then select the Jump to link in the search results. We'll take you to the screen where you can enter that info from your prior year return.

if you had a capital losses carryover from 2018 that needed to be entered on the 2019 return because you are required to use up to $3,000 in that year.  only what remains unused would be a carryforward to 2020.  if you used TurboTax for 2019 the carryforward data from 2018 would have transferred to 2019 and would have been used unless you delete the carryfoward info from the TurboTax worksheets.