This is a module script, it is in ServerScriptService:

local PlayerDataHandler = {}

local dataTemplate = {
    Race = "",
    Cash = 0,
    Inventory = {},
    Level = 0,
}

local ProfileService = require(game.ServerScriptService.ProfileService)
local Players = game:GetService("Players")

local ProfileStore = ProfileService.GetProfileStore("PlayerProfile", dataTemplate)

local Profiles = {}

local function playerAdded(player)
    repeat wait() until player:GetAttribute("slot") ~= nil

    local slot = player:GetAttribute("slot")
    print("Loaded with slot", slot)

    local profile = ProfileStore:LoadProfileAsync(slot .. player.UserId)

    if profile then
        if profile.Error then
            warn("Failed to load profile for player", player.UserId, "- Error:", profile.Error)
            player:Kick()
            return
        end

        profile:Reconcile()

        profile:ListenToRelease(function()
            Profiles[player] = nil
            if player:IsDescendantOf(Players) then
                print("Profile released for player", player.UserId, "- Kicking player.")
                player:Kick()
            end
        end)

        if not player:IsDescendantOf(Players) then
            profile:Release()
        else
            Profiles[player] = profile
            print("Loaded profile for player", player.UserId)
            print(Profiles[player].Data)
        end
    else
        print("Failed to load profile for player", player.UserId)
        player:Kick()
    end
end

function PlayerDataHandler:Init()
    for _, player in ipairs(game.Players:GetPlayers()) do
        task.spawn(playerAdded, player)
    end

    game.Players.PlayerAdded:Connect(playerAdded)

    game.Players.PlayerRemoving:Connect(function(player)
        if Profiles[player] then
            Profiles[player]:Release()
        end
    end)
end

local function getProfile(player)
    assert(Profiles[player], string.format("Profile does not exist for %s", player.UserId))

    return Profiles[player]
end

function PlayerDataHandler:Get(player, key)
    local profile = getProfile(player)
    assert(profile.Data[key], string.format("Data does not exist for key: %s", key))

    return profile.Data[key]
end

function PlayerDataHandler:Set(player, key, value)
    local profile = getProfile(player)
    assert(profile.Data[key], string.format("Data does not exist for key: %s", key))

    assert(type(profile.Data[key]) == type(value))

    profile.Data[key] = value
end

function PlayerDataHandler:Update(player, key, callback)
    local profile = getProfile(player)

    local oldData = self:Get(player, key)
    local newData = callback(oldData)

    self:Set(player, key, newData)
end

return PlayerDataHandler

This script calls the module module script and no errors occur:

local PlayerDataHandler = require(game.ServerScriptService:WaitForChild("PlayerDataHandler"))

script.Parent.Touched:Connect(function(hit)
    local player = game.Players:GetPlayerFromCharacter(hit.Parent)
    
    if player then 
        PlayerDataHandler:Update(player, "Cash", function(currentCash)
            return currentCash + 300
        end)
        
        PlayerDataHandler:Update(player, "Inventory", function(currentInventory)
            table.insert(currentInventory, "Bag")
            
            return currentInventory
        end)
        
        script.Parent:Destroy()
        
        print(PlayerDataHandler:Get(player, "Cash"))
        print(PlayerDataHandler:Get(player, "Inventory"))
    end
end)

This script is the one I have a problem with, it is in PlayerGUI and cannot locate the module script when I try to call it resulting in this error, Infinite yield possible on ‘StarterPlayer.StarterCharacterScripts:WaitForChild(“PlayerDataHandler”)’:
local TweenService = game:GetService(“TweenService”)

local tweenInfo = TweenInfo.new(
.1,
Enum.EasingStyle.Linear,
Enum.EasingDirection.Out
)

local tween = TweenService:Create(script.Parent.Parent.Slot2, tweenInfo, {Position = UDim2.new(0.661, 0, 0.126, 0)})
local tween2 = TweenService:Create(script.Parent.Parent.Slot2, tweenInfo, {Position = UDim2.new(0.681, 0, 0.126, 0)})

local tween3 = TweenService:Create(script.Parent.Parent.Slot3, tweenInfo, {Position = UDim2.new(0.122, 0, 0.126, 0)})
local tween4 = TweenService:Create(script.Parent.Parent.Slot3, tweenInfo, {Position = UDim2.new(0.102, 0, 0.126, 0)})

local right = script.Parent[“>”]
local left = script.Parent[“<“]

local tween5 = TweenService:Create(left, tweenInfo, {Position = UDim2.new(1.162, 0, 0.442, 0)})
local tween6 = TweenService:Create(left, tweenInfo, {Position = UDim2.new(1.062, 0, 0.442, 0)})
local tween7 = TweenService:Create(right, tweenInfo, {Position = UDim2.new(-0.292, 0, 0.442, 0)})
local tween8 = TweenService:Create(right, tweenInfo, {Position = UDim2.new(-0.192, 0, 0.442, 0)})

local isMouseOver = false
local isButtonClicking = false

script.Parent.MouseEnter:Connect(function()
if not isMouseOver then
isMouseOver = true

    local n = 157
    local n2 = 180

    right.TextTransparency = 0
    left.TextTransparency = 0
    script.Parent.Sound:Play()
    tween2:Play()
    tween4:Play()
    tween6:Play()
    tween8:Play()
    repeat
        right.TextTransparency -= 0.1
        left.TextTransparency -= 0.1
        task.wait(0.01)
    until right.TextTransparency <= 0 and left.TextTransparency <= 0 or not isMouseOver
end

end)

script.Parent.MouseLeave:Connect(function()
if isMouseOver then
isMouseOver = false

    right.TextTransparency = 1
    left.TextTransparency = 1
    tween:Play()
    tween3:Play()
    tween5:Play()
    tween7:Play()
end

end)

script.Parent.MouseButton1Click:Connect(function()
script.Parent.Biwa:Play()
if not isButtonClicking then
isButtonClicking = true

    -- Fade out the current slots and title
    repeat
        script.Parent.Parent.SlotsTitle.TextTransparency += 0.2
        script.Parent.Parent.Slot1.TextTransparency += 0.2
        script.Parent.Parent.Slot2.TextTransparency += 0.2
        script.Parent.Parent.Slot3.TextTransparency += 0.2
        script.Parent.Parent.Slot1.BackgroundTransparency += 0.2
        script.Parent.Parent.Slot2.BackgroundTransparency += 0.2
        script.Parent.Parent.Slot3.BackgroundTransparency += 0.2
        script.Parent.Parent.Back.TextTransparency += 0.2
        task.wait(0.01)
    until script.Parent.Parent.SlotsTitle.TextTransparency >= 1

    -- Hide current UI elements
    script.Parent.Parent.Visible = false

    -- Load PlayerDataHandler module
    local PlayerDataHandler = require(game.StarterPlayer.StarterCharacterScripts:WaitForChild("PlayerDataHandler"))

    local player = game.Players.LocalPlayer
    local race = PlayerDataHandler:Get(player, "Race")

    if race ~= "" then
        print("Selection")
    else
        print("Not selected")
    end
end

end)

The first block of code is the actual module script, the second calls that script and works just fine, but the last has problems and causes an error. I suspect it has to do with them being server and client side scripts but I’m not sure how to fix that issue. Thank you in advance