why has it stopped me being able to look left and right?

hi im a begginer and im following a tutorial made by brackeys and im confused on why it has stopped me being able to look left and right.

heres the code.

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

public class mouselook : MonoBehaviour
{
public float mouseSensitivity = 100f;

public Transform playerBody;

float xRotation = 0f;

void Start()
{
    Cursor.lockState = CursorLockMode.Locked;
}

// Update is called once per frame
void Update()
{
    float mouseX = Input.GetAxis("Mouse X") * mouseSensitivity * Time.deltaTime;
    float mouseY = Input.GetAxis("Mouse Y") * mouseSensitivity * Time.deltaTime;

    xRotation -= mouseY;
    xRotation = Mathf.Clamp(xRotation, -90f, 90f);

    transform.localRotation = Quaternion.Euler(xRotation, 0f, 0f);
    playerBody.Rotate(Vector3.up * mouseX);
}

}

You clamped the wrong axis.

X is usually horizontal
Y is vertical

So, probably this will fix your problem

void Update()
 {
     float mouseX = Input.GetAxis("Mouse X") * mouseSensitivity * Time.deltaTime;
     float mouseY = Input.GetAxis("Mouse Y") * mouseSensitivity * Time.deltaTime;
     yRotation -= mouseY;
     yRotation = Mathf.Clamp(yRotation, -90f, 90f);
     transform.localRotation = Quaternion.Euler(0f, yRotation, 0f);
     playerBody.Rotate(Vector3.up * mouseY);
 }