Why does unity not see monobehaviour?

I was working on a game, and everything worked fine, until i restarted Unity and every script said it had no monobehaviour.
PLS help!

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
{
}