question

I get the error: "InvalidParams" - "Invalid input params" after I click the Authorize button on the Steam Purchase overlay.

private void PurchaseCoins()
  {
    PlayFabClientAPI.StartPurchase(new StartPurchaseRequest()
    {
      CatalogVersion = "Avatar Items",
      Items = new List<ItemPurchaseRequest>()
      {
        new ItemPurchaseRequest()
        {
          ItemId = "IAP_1Dollar",
          Quantity = 1,
          Annotation = "Purchased via in-game store"
        }
    }
    }, result =>
    {
      text.text += Environment.NewLine + "StartPurchase: " + result.OrderId;
      Debug.Log("StartPurchase");
      PurchaseOnSteam(result.OrderId);
    }, error =>
    {
      text.text += Environment.NewLine + "StartPurchase FAILED";
      Debug.Log("StartPurchase FAILED: " + error.ErrorMessage);
    });
  }


  private void PurchaseOnSteam(string orderId)
  {
    PlayFabClientAPI.PayForPurchase(new PayForPurchaseRequest()
    {     
      OrderId = orderId,
      ProviderName = "Steam",
      Currency = "RM"
    }, result => {
      text.text += Environment.NewLine + "Purchase on steam";
    }, error => {
      text.text += Environment.NewLine + "SENT TO STEAM FAILED";
    });
  }


  private void OnSteamApproval(MicroTxnAuthorizationResponse_t pCallback)
  {
    if (pCallback.m_bAuthorized == 1)
    {
      text.text += Environment.NewLine + "Authorized Payment: " + pCallback.m_ulOrderID.ToString();


      ConfirmPurchase(pCallback.m_ulOrderID);
    }
    else
    {
      text.text += Environment.NewLine + "Failed to authorize payment";
      // Player didn't authorize the payment
      Debug.Log("Failed to authorize payment");
    }
  }


  private void ConfirmPurchase(ulong orderId)
  {
    PlayFabClientAPI.ConfirmPurchase(new ConfirmPurchaseRequest()
    {
      OrderId = orderId.ToString()
    }, result => 
    {
      text.text += Environment.NewLine + "CONFIRMED PURCHASE";
    }, error => 
    {
      text.text += Environment.NewLine + "FAILED: " + error.Error;
      text.text += Environment.NewLine + error.ErrorMessage;
    });
  }

Not sure what's wrong?