Why do I keep getting the "the script needs to derive from monobehavior" error?

I’m very new to Unity, game development, coding, all of it really. I thought I’d try cloning a game from watching a YouTube video and following it step by step, which I thought will help me understand the basics of things. So this code below is an exact copy of what a YouTuber wrote, which worked fine for him but not me. Also note: The script title and the name after “class” are identical, so that’s not the problem. Please tell me why else this error may occur, if I have a typo in the code that I’m unaware of, etc. I’d appreciate help so much as I’ve been stuck on this for days now.

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

[RequireComponent(typeof(Rigidbody2D))]
public class TapController : MonoBehaviour {

    public float tapForce = 10;
    public float tiltsmooth = 5;
    public Vector3 startPos;
   
    Rigidbody2D rigidbody;
    Quaternion downRotation;
    Quaternion forwardRotation;
   
    void Start() {
        rigidbody = GetComponent<Rigidbody2D>();
        downRotation = Quaternion.Euler(0, 0, -90);
        forwardRotation = Quaternion.Euler(0, 0, 35);
       
    }
   
    void Update() {
        if (Input.GetMouseButtonDown(0)) {
            transform.rotation = forwardRotation;
            rigidbody.AddForce(Vector2.up * tapForce, ForceMode2D.Force);
        }
       
        transform.rotation = Quaternion.Lerp(transform.rotation, downRotation, tiltSmooth * Time.deltaTime);
    }
  
    void OnTriggerEnter2D(Collider2D col) {
        if (col.gameObject.tag == "ScoreZone") {
            //register a score event
            //play a sound
        }
       
        if (col.gameObject.tag == "DeadZone") {
            rigidbody.simulated = false;
            //register a dead event
            //play a sound
        }
    }
}

check your console and see if you have some other errors there as well

Is your “MonoBehavior” test white color? If it is, it’s possible that something got broken. Try reloading the solution (File > Close Solution. After that just open it again). Maybe it fixes your issue.