cant jump well on moving platform

hello guys my character cant jump well on moving platform. when i press Space on other ground, my character will jump smooth, the GetButton works very well and Sensitive, but here is the problem, when i stand on moving platform , my Space always cant work very well, i tried to debug it , i cant fix it , pls help me , thx lot.

here is my character C#

     public GameObject Dog;
     private float my_runspeed = 8; 
     private float my_jumpHeight = 800; 
     private Animator my_ani; 
     private bool Jumping = false;  
     private bool IsGround = false; 
 
     void Awake () {
         my_body = GetComponent<Rigidbody2D> ();  
         my_ani = GetComponent<Animator>();  
     }
 
 
     void FixedUpdate () {
                 MyJump();
                 MyMove ();
         My_StateMachine ();
         my_JumpState ();
     }
 
 
     void MyMove () {
         float myxy = Input.GetAxis ("Horizontal");  
         my_body.velocity = new Vector2 (myxy * my_runspeed, my_body.velocity.y);  
 
         if (myxy != 0) {  
             float my_Scale_X = Mathf.Sign (my_body.velocity.x) == 1 ? 1 : -1; 
             Dog.transform.localScale = new Vector3 (my_Scale_X, 1, 1);
         }
     }
 
 
     void MyJump () {
         if (!IsGround != false || my_body.velocity.y != 0) {return;}  
 
         if (Input.GetButton("Jump")) {
             Debug.Log(my_body.velocity); 
             my_body.AddForce (Vector3.up * my_jumpHeight);  //Vector3.up = (0,1,0)
         }        
     }
 
 
     void My_StateMachine () {
         my_ani.SetFloat ("Speed", Mathf.Abs (my_body.velocity.x));  
         my_ani.SetBool("Jumping", Jumping); 
         my_ani.SetBool("IsGround", IsGround);  
     }
 
 
     void my_JumpState () {
         if (my_body.velocity.y > 0.1f) { 
             Jumping = true;
             IsGround = false;
         }else if(Jumping){
             Jumping = false;
         }
     }
 
 
     void OnCollisionEnter2D(Collision2D coll)
     {
         if (coll.gameObject.tag == "Ground" && coll.contacts[0].normal == Vector2.up) {
             IsGround = true;
         }

here is setParent

    private Transform Target;  
     public GameObject Character;  
     public GameObject Platform;  
     void OnCollisionEnter2D(Collision2D coll)  { 
         if(coll.gameObject.tag == "Player" && coll.contacts[0].normal == -Vector2.up) 
         {                                                                             
             Target = coll.gameObject.transform; 
             Target.SetParent(Platform.gameObject.transform);  
         }
     }
 
     void OnCollisionExit2D(Collision2D coll)  { 
         if(coll.gameObject.tag == "Player")  
         {
             Target = coll.gameObject.transform;  
             Target.SetParent(Character.gameObject.transform);  
         }
     }
 
 }

here is moving platform

     public GameObject Platform;  
     public float min;  
     public float max; 
     private float Position_now; 
     private bool Move = true;  
     public float speed = 1f;  
 
     void Update() {
 
         Position_now = Platform.gameObject.transform.localPosition.x; 
         if (Move == true) { 
             Platform.transform.localPosition += new Vector3(speed, 0, 0); 
             if (Position_now >= max) {  
                 Move = false;
             }
         }
    
         if (Move == false) {
             Platform.transform.localPosition += new Vector3(-speed, 0, 0); 
             if (Position_now <= min) { 
                 Move = true;
             }
         }
     }
 
 }