When I fire an event that prompts the user to buy an item after buying an item, it's nil, help?

Everytime I try to fire an event from a script then I call that event to prompt a user to buy an item once they bought an item, it always comes up with this error "Argument 2 missing or nil".

Here are my scripts:

ServerScriptService>PurchaseModelHandler

local folder = game.ReplicatedStorage.PurchasedModels
local player = game.Players.LocalPlayer

local counterid = 1272040120
local lampid = 1272039316

folder.Counter.OnClientEvent:connect(function(player)
    wait(3)
    game:GetService("MarketplaceService"):PromptPurchase(counterid, player)
end)

folder.Lamp.OnClientEvent:connect(function(player)
    wait(3)
    game:GetService("MarketplaceService"):PromptPurchase(lampid, player)
end)

ServerScriptService>PurchaseHandler

local marketServ = game:GetService("MarketplaceService")
local folder = game.ReplicatedStorage.PurchasedModels

local modelBuy1 = 126893799 -- Counter
local modelBuy2 = 126893609 -- Lamp

marketServ.ProcessReceipt = function(receiptInfo)
    for i, player in ipairs(game.Players:GetChildren()) do
        if player.userId == receiptInfo.PlayerId then
            if receiptInfo.ProductId == modelBuy1 then
                folder.Counter:FireClient(player)
            elseif receiptInfo.ProductId == modelBuy2 then
                folder.Lamp:FireClient(player)
            end
        end
    end
    return Enum.ProductPurchaseDecision.PurchaseGranted
end

Here are all my events: https://gyazo.com/65d345303b49752a37bd5fa81906c3ad

I've tried: RemoveEvents, BindableFunctions, BindableEvents, RemoteFunctions, all came up either: "Argument 2 missing or nil" or an error about ":OnClientInvoke()" or ":OnServerInvoke()".

Please help!