Cannot enable The Nest or Shen's Last Gift missions.

I love XCOM2 and want to finally take on a Legendary Ironman run but I just know the rulers are going to give me a bad time. I want to enable the mission so I can keep them on the back burner until I'm ready for them but no matter what I do the mission is never enabled. I make the sure the box is checked every time I load a new game, I've deleted my game folder in My Documents and rebuilt the config, I've even unsubscribed from all mods and reinstalled the game from scratch but all to no avail. Does anyone know a fix for this? Is there an option in the INIs somewhere that will let me enable them after the campaign has started? Thanks in advance!

EDIT: I finally solved it for anyone curious. I'm not entirely sure what data the game saves to the steam cloud, but enabling cloud saves will continue to cause this error no matter what you do. Turning off steam cloud, deleting your Config folder, and doing a game file verification will fix the bug and allow you to play the missions again.