Why does this local script doesn't work outside of build mode?

Player = game.Players.LocalPlayer
Menu = script.Parent
Play = Menu.Play
About = Menu.About
HasPressedPlay = false
Info = script.Parent.Info
Close = Info.Close

function MouseEnterPlayButton()
    Play.FontSize = "Size36"
    Play.BackgroundColor3 = Color3.new(0.1, 0.65, 0.71)
    Play.Size = UDim2.new(0.45, 0, 0.225, 0)
end

function MouseLeftPlayButton()
    Play.FontSize = "Size24"
    Play.BackgroundColor3 = Color3.new(0.54, 0.62, 0.7)
    Play.Size = UDim2.new(0.3, 0, 0.15, 0)
end

function MouseEnterAboutButton()
    About.FontSize = "Size36"
    About.BackgroundColor3 = Color3.new(0.1, 0.65, 0.71)
    About.Size = UDim2.new(0.45, 0, 0.225, 0)
end

function MouseLeftAboutButton()
    About.FontSize = "Size24"
    About.BackgroundColor3 = Color3.new(0.54, 0.62, 0.7)
    About.Size = UDim2.new(0.3, 0, 0.15, 0)
end

function PlayGame()
    if HasPressedPlay == false then
        for GuiMove = 1, 30 do
            if GuiMove <= 20 then
                Play.Position = Play.Position +UDim2.new(0.05, 0, 0, 0)
            end
            if GuiMove >=  10 then
                About.Position = About.Position +UDim2.new(0.05, 0, 0, 0)   
            end
            wait()  
        end
        Menu:remove()       
    end
end

function CloseInfo()
    Info.Visible = false
end

function InfoPopup()
    if Info.Visible == false then
    Info.Visible = true
    else
        Info.Visible = false
    end
end


About.MouseButton1Down:connect(InfoPopup)
Close.MouseButton1Down:connect(CloseInfo)
About.MouseLeave:connect(MouseLeftAboutButton)
About.MouseEnter:connect(MouseEnterAboutButton)
Play.MouseLeave:connect(MouseLeftPlayButton)
Play.MouseEnter:connect(MouseEnterPlayButton)
Play.MouseButton1Down:connect(PlayGame)