Script Creation Issue - using ... / Monobehaviour is not activating

Hello,

When I create a new script, the following statements are not activing properly.

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class Arrays : MonoBehaviour

I was creating scripts without issue before. I feel like a setting changed.

Specifically:

// these were greyed out 
using System.Collections;
using System.Collections.Generic;

// Monobehaviour was blue
public class Arrays : MonoBehaviour

I fixed it the first time by manually typing out:

using System.Collections;
using System.Collections.Generic;

This no longer works.

This has resolved itself.

Check compiling errors on scripting files.