What have I done wrong with this DataStore script?

Here is a Script and a ModuleScript. There are two reason that I am using a ModuleScript: 1st it allows you to have shared code between several scripts (code once use many times), 2nd I had already written it.

So here it is:

Structure of game.ServerScriptService

--game
    --ServerScriptService
        --DS            --ModuleScript
        --StatControl   --Script

Module script in game.ServerScriptService

--Created by shadownetwork
--Created 02/21/2017
--Last Edited 02/21/2017

--DataStore API

--Accepts
    --Store as string
    --Key as string
    --Value as number, boolean, string, or Lua table
    --UpdateData only takes Value as number

--Examples
--  require(workspace.DS):SetData("PlayerIDToName", 1, "Roblox")
--  PlayerName = require(_G.M.DS):GetData("PlayerIDToName", 1)
--  require(workspace.DS):ForceSetData("PlayerIDToName", 1, "WrongName")
--  PlayerName = require(_G.M.DS):GetData("PlayerIDToName", 1)
--  require(workspace.DS):UpdateData("Stats", "Visits", +1)

local DataStoreService = game:GetService('DataStoreService')

T = {DataStoreRetries = 5}

function T:GetData(Store, Key) -- Checks to see if data exist
    Data = nil
    if Store and Key then
        --print("Getting Data")
        local tries = 0
        repeat
            tries = tries + 1
            success, message = pcall(function() 
                DataStore = DataStoreService:GetDataStore(Store)
                Data = DataStore:GetAsync(Key)
            end)
            if not success then
                wait(1)
            end
        until tries == T.DataStoreRetries or success
        if not success then
            print("")
            print("require(_G.M.DS):GetData, Error Data not loaded from DataStore")
            print("Current values: Store = "..Store..", Key = "..Key)
            error(message)
        end
    end
    return Data
end

function T:SetData(Store, Key, Value) -- Sets data if it doesn't exist
    if Store and Key and Value then
        --print("Setting Data")
        local tries = 0
        repeat
            tries = tries + 1
            success, message = pcall(function() 
                DataStore = DataStoreService:GetDataStore(Store)
                if not T:GetData(Key) then
                    DataStore:SetAsync(Key, Value)
                end
            end)
            if not success then
                wait(1)
            end
        until tries == T.DataStoreRetries or success
        if not success then
            print("")
            print("require(_G.M.DS):SetData, Error Data not saved to DataStore")
            print("Current values: Store = "..Store..", Key = "..Key..", Value = "..Value)
            error(message)
        end
    end
end

function T:ForceSetData(Store, Key, Value) -- Overwrites old data
    if Store and Key and Value then
        --print("Overwriting Data")
        local tries = 0
        repeat
            tries = tries + 1
            success, message = pcall(function() 
                DataStore = DataStoreService:GetDataStore(Store)
                DataStore:SetAsync(Key, Value)
            end)
            if not success then
                wait(1)
            end
        until tries == T.DataStoreRetries or success
        if not success then
            print("")
            print("require(_G.M.DS):ForceSetData, Error Data not saved to DataStore")
            print("Current values: Store = "..Store..", Key = "..Key..", Value = "..Value)
            error(message)
        end
    end
end

function T:UpdateData(Store, Key, Value) -- Updates number and int values
    if Store and Key and Value then
        --print("Updating Data")
        local tries = 0
        repeat
            tries = tries + 1
            success, message = pcall(function() 
                DataStore = DataStoreService:GetDataStore(Store)
                DataStore:UpdateAsync(Key, function(OldValue)
                    OldValue = OldValue or 0
                    local NewValue = OldValue
                    if type(Value) == "number" then
                        NewValue = NewValue + Value
                    end
                    return NewValue
                end)
            end)
            if not success then
                wait(1)
            end
        until tries == T.DataStoreRetries or success
        if not success then
            print("")
            print("require(_G.M.DS):UpdateData, Error Data not saved to DataStore")
            print("Current values: Store = "..Store..", Key = "..Key..", Value = "..Value)
            error(message)
        end
    end
end

return T

Script in game.ServerScriptService

local DataStore = game:GetService("DataStoreService")
local ds1 = DataStore:GetDataStore("Currency")
ID = "player"

game.Players.PlayerAdded:connect(function(player)
    local stats = Instance.new("Folder",player)
    stats.Name = "leaderstats"
    local Schmeckles = Instance.new("IntValue",stats)
    Schmeckles.Name = "Schmeckles"

    local key = ID..player.userId
    Schmeckles.Value = require(game.ServerScriptService.DS):GetData("Currency", key) or 0
end)

 game.Players.PlayerRemoving:connect(function(player)
    local key = ID..player.userId
    require(game.ServerScriptService.DS):ForceSetData("Currency", key, player.leaderstats.Schmeckles.Value)
end)

while wait(60) do
    P = game:GetService("Players"):GetChildren()
    for i=1, #P do
        if P[i]:FindFirstChild("leaderstats") then
            if P[i].leaderstats:FindFirstChild("Schmeckles") then
                local key = ID..P[i].userId
                require(game.ServerScriptService.DS):ForceSetData("Currency", key, P[i].leaderstats.Schmeckles.Value)
            end
        end
    end
end

game.OnClose = function()
    wait(10)
end