What did I do wrong with this Remote Function?

I am using FE for the first time, and I have a shop GUI. In workspace, there is a script called BuyProductHandler. In the GUI button, there's a local script.

This is the BuyProductHandler script:

script.BuyProduct.OnServerInvoke:connect(function(plr, itemname, price)
	
	local stats = plr:FindFirstChild("leaderstats")
	local inventory = plr:FindFirstChild("Inventory")
	local item = inventory:FindFirstChild(itemname)
	local money = stats:FindFirstChild("Z-Coins")
	
	if money.Value >= price then
		
		money.Value = money.Value - price
		item.Value = true
		return true
		
	else
		return false
	
	end
end)

script.PlayerHasItem.OnServerInvoke:connect(function(plr, itemname)
	
	local inventory = plr:FindFirstChild("Inventory")
	local item = inventory:FindFirstChild(itemname)
	
	if item.Value == true then
		
		return true 
	else
		return false
		
	end
	
	
end)

script.Equip.OnServerInvoke:connect(function(plr, itemname, itemtype)
	
	local inventory = plr:FindFirstChild("Inventory")
	local item = inventory:FindFirstChild(itemname)
	local itempath = game.Lighting.PurchaseObjects:FindFirstChild(itemtype)
	local obj_item = itempath:FindFirstChild(item)
	
	if itemtype == "effect" then
		
		obj_item:Clone().Parent = plr.Character.Torso
	
	elseif itemtype == "weapon" then
		
			obj_item:Clone().Parent = plr.Backpack
		
	elseif itemtype == "hat" then
		
			obj_item:Clone().Parent = plr.Character
		
	end
	
end)

This is the local script:

price = 40
item = script.Parent.Parent.Name
Handler = workspace.BuyProductHandler
t = "effect"

script.Parent.MouseButton1Click:connect(function()
	
	if Handler.PlayerHasItem:InvokeServer(game.Players.LocalPlayer, item) == true then
		
		Handler.Equip:InvokeServer(game.Players.LocalPlayer, item, t)
		
	else
		
		if Handler.BuyProduct:InvokeServer(game.Players.LocalPlayer, item, price) == true then
			
			Handler.Equip:InvokeServer(game.Players.LocalPlayer, item, t)
			
		end
		
	end
	
	
end)

Here is the console:

18:33:30.716 - OnServerInvoke is a callback member of RemoteFunction; you can only set the callback value, get is not available 18:33:30.719 - Stack Begin 18:33:30.721 - Script 'Workspace.BuyProductHandler', Line 1 18:33:30.723 - Stack End