Looks like the update is calling a method only once

Hey all I have got a trigger area that when the player enters it sets a bool in the player true that then makes pop-up an image using some static functions I made in a static utility class.The problem is that it calls only once or not at all these functions,the strange thing is that I already used them and they work fine. Here the class with the utility functions

 public static class UtilityFunctions {
 
     //mostra l'immagine
     public static void ShowImage(Image img,float increase_scale)
     {
         if (img.rectTransform.localScale.x < 1 && img.rectTransform.localScale.y < 1 && img.rectTransform.localScale.z < 1)
         {
             img.rectTransform.localScale += new Vector3(increase_scale, increase_scale, increase_scale);
         }
     }
 //there are other functions but that's what I'm using...
 }

Here the simple script that makes pop up the image:

 public class InteractableActive : MonoBehaviour {
 
     GameObject player;
     bambina_inputs bambina_inputs;
     public Image interactable_img;
     //Image interactable_button_img;
     public float grandezza_rate;
     int a=0;
 
     // Use this for initialization
     void Start () {
         player = GameObject.Find("bambina");
         bambina_inputs = player.GetComponent<bambina_inputs>();        
     }
 
     // Update is called once per frame
     void Update () {
         //ingrandisce l'immagine,la fa apparire
         if(bambina_inputs.can_interact)
         {
             /*UtilityFunctions.ResizeImage(interactable_img, UtilityFunctions.scelta.ingrandisci, 1, grandezza_rate, false); it is called once*/
             UtilityFunctions.ShowImage(interactable_img, grandezza_rate);//it isn't called at all
             Debug.Log("hey");//it is called normally
         }
     }
 }
 

The class with the utility functions aren't in any gameobjects in the scene. The funniest thing is that I've got other scripts in other gameobjects that use these functions a lot of times and they work fine and they are normally called at each frame.What's wrong? What I must change to make it call these functions? I've been crashing my head on the keyboard for a lot of time,I really hope someone helps me. Thank you in advance :D