Inventory adds an item only once.

I have been following a youtube channel called Sykoo on how to make an inventory in unity and when I tested the code that I had written it seemed to work (although the game object item was added to both of my raw images) and the item was added to my inventory. After I exited the game and returned to it again it did not add to my inventory. Any help would be great thank you.Here is the code (if ive made a glaring mistake I may not have noticed it as Im a beginner to unity and sorry there is 3 scripts that make my inventory so there is a lot of code):

     void Start()
     {
         inputDown = 0;
         slots = slotHolder.transform.childCount;
         slot = new Transform[slots];//Limit of slots //Slot is a new arra. Going to be amount of slots there are.
         DetectInventorySlots();
     }
   

     public void OnTriggerEnter(Collider other)
     {
         if (other.GetComponent<Item>())
         {
             itemPickedUp = other.gameObject;
             AddItem(itemPickedUp);
             
         }
     }
     public void OnTriggerExit(Collider other)
     {
         if(other.GetComponent<Item>()) {
             
             itemAdded = false;
             
 
         }
     }
     public void AddItem(GameObject item)
     {
         for (int i =0; i < slots; i++) //Check for each slot. this is a regular for loop that is created.
         {
             if (slot[i].GetComponent<Slot>().empty==false && itemAdded==false)//If the slot is empty
             {
                 slot[i].GetComponent<Slot>().item = itemPickedUp;
                 slot[i].GetComponent<Slot>().itemIcon = itemPickedUp.GetComponent<Item>().icon;
                 itemAdded = true;
             }
 
         }
     }
     public void DetectInventorySlots()
     {
         for(int i = 0; i<slots; i++)//check for loop with integer called i at start. while i is lower then slots going to increase i by 1
         {
             slot[i] = slotHolder.transform.GetChild(i);//
             print(slot[i].name);//print amount of slots
         }
     }
 }
 The second "Slot" script:
         void Update()
         {
             if (item && itemIcon)
             {
                 empty = false;//If there is an item empty is going to be false
                 itemIcon = item.GetComponent<Item>().icon; //the items icon is equal to the icon of that gameobject
                 this.GetComponent<RawImage>().texture = itemIcon; //The slots texture is equal to itemIcon (which is a texture)
             }
             else
             {
                 empty=true;
             }
             
         }
 
     
     }
 

The last script that is applied to the weapon (Item):

     public string type; //Type of item
     public int ID;
     public string description;
     public Texture icon;
     public bool pickedUp;