Skybox disappears after I switch scene

The title says it: After I switch scenes, the skybox just disappears. But only the material I selected. The default skybox never disappears. Does anyone know what I could do?

Edit: Just saw that the directional Light wasn‘t working too.

Which version of unity are you using, and is this happening inside the editor or on a standalone build?
Although it’d be a very simple mistake, you can check your camera on your other scene. It may be set to display something other than a skybox on clear flags. Also make sure your lighting is built.