Fog Not Working, Shadows No Longer Cast
Went through the video about 10 times & still can't get something right. My settings are a little different than yours but I stuck to the tutorial methods very closely. The fog has never looked right & the scene shading doesn't look very similar to yours. Your viewport looks far better than my fully-rendered 90% product. The lighting & shadows of surrounding trees has never been good, the trees look dull whereas I can see a gradient of shadows on your tree trunks, clear god-rays through fog. My shadows aren't even in the scene. What's happening here?
Here's a link for the .blend: