To rebuild lighting hit the drop down arrow next to “Build” in the main toolbar and select “Build Lighting Only.” Alternatively you can just hit the “Build” button on the main toolbar.
I just found this about the exclamation marks in the scene outliner: Outliner in Unreal Engine | Unreal Engine 5.1 Documentation
The exclamation marks are indicators of the mobility type of the actors.
If the fog isn’t showing I would recommend clicking on it in the scene outliner and then in the “Details” panel under the “Rendering” section make sure the checkbox next to “Visible” is checked.