[PLEASE HELP] When LeftShift is pressed when the character is on ground he dont jump

When LeftShift is pressed when the character is on ground he dont jump (but he run when is on air), i tried so many things and still not working

Code:

      if (Input.GetKeyDown(KeyCode.LeftShift))
     {
         speed = normalSpeed * speedMultiplyer;
     }
      if (Input.GetKeyUp(KeyCode.LeftShift))
     {
         speed = normalSpeed;

     }

       if (Input.GetKeyDown("space"))
     {
         Jump();
     }

Entire code:

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

public class PlayerMovement : MonoBehaviour { Animator animator; CharacterController controller; public Transform cam; public Transform groundCheck; public float groundDistance = 111f; public LayerMask groundMask;

 public float normalSpeed = 6f;
 public float speedMultiplyer = 3f;
 float speed;

 public float jumpForce = 4f;
 public float jumpTimes = 6f; 
 public float gravityForce = -9.81f;

 public float turnSmoothTime = 0.1f;
 float turnSmoothVelocity; 

 int animationState = 0;

 Vector3 velocity;
 public bool isGrounded;

 private void OnEnable() 
 {
     speed = normalSpeed;
     animator = GetComponent<Animator>();
     controller = GetComponent<CharacterController>();
 }

 void Update()
 {    

     isGrounded = Physics.CheckSphere(groundCheck.position, groundDistance, groundMask);

     if(isGrounded && velocity.y < 0)
     {
         velocity.y = -2f;
     }

     velocity.y += gravityForce * Time.deltaTime;
     controller.Move(velocity * Time.deltaTime);

     float horizontal = Input.GetAxisRaw("Horizontal");
     float vertical = Input.GetAxisRaw("Vertical");
     Vector3 direction = new Vector3(horizontal, 0f, vertical).normalized;

     if (direction.magnitude >= 0.1f)
     {
         Move(direction);
     
         if (speed > normalSpeed)
         {
         animationState = 2;
         ChangeAnimation();
          }else
           {
         animationState = 1;
         ChangeAnimation();
          }

     }else
     {        
         animationState = 0;
         ChangeAnimation();
     }

     //Correr
      if (Input.GetKeyDown(KeyCode.LeftShift))
     {
         speed = normalSpeed * speedMultiplyer;
     }
      if (Input.GetKeyUp(KeyCode.LeftShift))
     {
         speed = normalSpeed;

     }

       if (Input.GetKeyDown("space"))
     {
         Jump();
     }
 }

 //Movimentação
 void Move(Vector3 direction)
 {
         float targetAngle = Mathf.Atan2(direction.x, direction.z) * Mathf.Rad2Deg + cam.eulerAngles.y;
         float angle = Mathf.SmoothDampAngle(transform.eulerAngles.y, targetAngle, ref turnSmoothVelocity, turnSmoothTime);
         transform.rotation = Quaternion.Euler(0f, angle, 0f);
         Vector3 moveDir = Quaternion.Euler(0f, targetAngle, 0f) * Vector3.forward;
         controller.Move(moveDir.normalized * speed * Time.deltaTime);
 }
 
 //Pulo
  void Jump()
 {
     velocity.y = Mathf.Sqrt(jumpForce * -2f * gravityForce);
 }

 //Mudar Animação
 void ChangeAnimation()
 {
     if (animationState == 0)
     {
      animator.SetFloat("move",0f);
     }
      if (animationState == 1)
     {
         animator.SetFloat("move",0.2f);
     }
      if (animationState == 2)
     {
         animator.SetFloat("move",1f);
     }

 }

}