your file doesn't work, neither 2.7 or 2.8 will read it for some reasonIf you load a full save you will miss out the new content. what you want is not a full save, you want an "old content save" that starts you right before new content.
Well, I don't quite have that. as there was stuff i never did in the old content.
And I overwrote my "main" save. but i do have a save with 19 hours of playtime which is a little before the new content.
attached it. hopefully it helps you.