Answer by lodendsg

Reasons may be you have spaces in the names of the files or otherwise the name is not exsact ....

"CameraController.cs" is what it should be not "Camera Controller.cs" The name must match exactly ... case and whitespace included. I cant quite tell from your image on my device but that would be the first thing I checked.

Also I strongly recommend you put your classes in a namespace
using UnityEngine; namespace MyNamespace { public class CameraController : MonoBehaviour { //.... your code goes here } }

the MyNamespace is just an example ... you should generally name your namepsace something unique ... we usually use namespace HeathenEngineering.GameName { }