storing or loading from data store not working, why?

i am trying to save player data to data store using a script i found and modified The original script is from this website

I modified it so that it would store three values Experience as IntValue Rank as StringValue Bucks as IntValue

before i modified the script it worked but now it doesn't work anymore, i wonder have i referenced the data i want to store correctly?

my modified script is beloew

-- Data Storage
local DataStoreService = game:GetService("DataStoreService")

local playerData = DataStoreService:GetDataStore("PlayerData")



local function onPlayerJoin(player)  -- Runs when players join

    local leaderstats = Instance.new("Folder")  --Sets up leaderstats folder

    leaderstats.Name = "leaderstats"

    leaderstats.Parent = player

    local bucks = Instance.new("IntValue") --Sets up value for leaderstats

    bucks.Name = "Bucks"

    bucks.Parent = leaderstats

    local exp = Instance.new("IntValue") --Sets up value for leaderstats

    exp.Name = "Experience"

    exp.Parent = leaderstats


    local rank = Instance.new("StringValue") --Sets up value for leaderstats

    rank.Name = "Rank"

    rank.Parent = leaderstats



    local playerUserId = "Player_" .. player.UserId  --Gets player ID

    local data = playerData:GetAsync(playerUserId)  --Checks if player has stored data

    if data then

        bucks.Value = data['Bucks']

        exp.Value = data['Experience']

        rank.Value = data['Rank']

    else

        -- Data store is working, but no current data for this player

        bucks.Value = 50

        exp.Value = 50

        rank.Value = "Rec"

    end

end



local function create_table(player)

    local player_stats = {}

    for _, stat in pairs(player.leaderstats:GetChildren()) do

        player_stats[stat.Name] = stat.Value

    end

    return player_stats

end



local function onPlayerExit(player)  --Runs when players exit



    local player_stats = create_table(player)

    local success, err = pcall(function()

        local playerUserId = "Player_" .. player.UserId

        playerData:SetAsync(playerUserId, player_stats) --Saves player data

    end)



    if not success then

        warn('Could not save data!')

    end

end



game.Players.PlayerAdded:Connect(onPlayerJoin)

game.Players.PlayerRemoving:Connect(onPlayerExit)