Save data from an updated version of Middle-earth: Shadow of War is NOT backwards compatible with earlier versions of the game, including the base version.
On Xbox One or Windows 10 UWP if you uninstall an updated version of the game and then attempt to play an earlier version, including the base version, all of your existing save data will be permanently lost! Save data loss can also occur if playing a patched version of the game on Xbox One, and then attempting to play an earlier version of the game on Windows 10 UWP using the same account and vice-versa.
TO PREVENT SAVE LOSS, PLEASE NOTE THE FOLLOWING:
If you have uninstalled the game and wish to reinstall it, please be sure to update to the latest version BEFORE launching the game.
If you are playing the game on both Xbox One and Windows 10 UWP using the same account, please ensure you are playing the latest version of the game on both platforms.
If you believe your save file was affected by this issue, please contact WB Games Support.