Can't jump in C#

Hello, I have a problem with my character movement script in C#. I can walk, run, the gravity works great, but I can't jump. Here is the code :`using UnityEngine; using System.Collections;

[RequireComponent(typeof(CharacterController))]

[System.Serializable] public class Move { public bool enabled = true; public float walkSpeed = 5.0f; public float runSpeed = 10.0f; public KeyCode runKey = KeyCode.LeftShift; }

[System.Serializable] public class Jump { public bool enabled = true; public float height = 5.0f; public KeyCode jumpKey = KeyCode.Space; }

[System.Serializable] public class Gravity { public bool enabled = true; public float gravityForce = 5.0f; }

public class Controller : MonoBehaviour { public CharacterController characterController;

 private float horizontalAxis;
 private float verticalAxis;

 public Move move;
 public Jump jump;
 public Gravity gravity;

 void Update()
 {
     horizontalAxis = Input.GetAxis("Horizontal");
     verticalAxis = Input.GetAxis("Vertical");

     if(characterController.isGrounded)
     {
         Move(move.enabled, move.walkSpeed, move.runSpeed, move.runKey);
         Jump(jump.enabled, jump.height, jump.jumpKey);
     }
     Gravity(gravity.enabled, gravity.gravityForce);
 }

 public void Move(bool enabled, float walkSpeed, float runSpeed, KeyCode runKey)
 {
     Vector3 moveDirection = new Vector3();
     float speed = 0;

     if(enabled == true)
     {
         moveDirection = new Vector3(horizontalAxis, 0, verticalAxis);
         if(Input.GetKey(runKey))
         {
             speed = runSpeed;
         }
         if(!Input.GetKey(runKey))
         {
             speed = walkSpeed;
         }
         moveDirection *= speed;
         moveDirection = transform.TransformDirection(moveDirection);
         characterController.Move(moveDirection * Time.deltaTime);
     }
 }

 public void Jump(bool enabled, float jumpHeight, KeyCode jumpKey)
 {
     Vector3 moveDirection = new Vector3();

     if (enabled == true)
     {
         if(Input.GetKey(jumpKey))
         {
             moveDirection.y = jumpHeight;
         }
         characterController.Move(moveDirection * Time.deltaTime);
     }
 }

 public void Gravity(bool enabled, float gravityForce)
 {
     Vector3 moveDirection = new Vector3();

     if(enabled == true)
     {
         moveDirection.y -= gravityForce;
         characterController.Move(moveDirection * Time.deltaTime);
     }
 }

}`