Thanks for the response.

I dug a bit deeper and found a worksheet listing the losses going back to 2013. No carry forward had ever been taken. I entered the amount I needed to use and it came out of 2013. I decided not to amend any prior year, just take the NOL for 2020. Good exercise in NOL for me. I generally do not do C Corps but this was a friend/client that I do other tax work for and he was in a bind to get it done.