Need help with this error I'm only getting on Online mode...?

Hi there,

I've made this script for an intro GUI when a player joins the game, the only thing that's not working properly is the variables... The script works perfectly while testing it on Play Solo, but while testing on Online mode, it gives me an error:

'arrowZL is not a valid member of ScreenGUI'

It then references to the script's location inside my PlayerGUI then inside the ScreenGUI that I renamed.

Even after resetting in-game, it still occurs and gives the same error. No GUIs appear in-game at all.

Apologies for the length of the script, I thought it was necessary if I was going to get any help whatsoever with this. All of this is contained within a local script.

firstZ = script.Parent.firstZ
secondZ = script.Parent.secondZ
arrowZL = script.Parent.arrowZL
arrowZR = script.Parent.arrowZR
openbool = script.Parent.open
rip = script.Parent.rip
player = game.Players.LocalPlayer

Assets = {155660360,155660378,155670319}

for _, asset in ipairs(Assets) do
     Game:GetService("ContentProvider"):Preload("http://www.roblox.com/asset/?id=" .. asset)
end

function load()
    wait(10)
    firstZ:TweenPosition(UDim2.new(0.5, -50, 0.5, -50), "Out", "Quart", 4)
    secondZ:TweenPosition(UDim2.new(0.5, -50, 0.5, -50), "Out", "Quart", 4)
    wait(6)
    firstZ:TweenPosition(UDim2.new(0.5, -50, 0.08, -50), "Out", "Quart", 4)
    secondZ:TweenPosition(UDim2.new(0.5, -50, 0.08, -50), "Out", "Quart", 4)
    wait(4)
    arrowZR.Visible = true
    arrowZL.Visible = true
    arrowZR:TweenPosition(UDim2.new(0.5, 52, 0.08, -12), "Out", "Quart", 1.5)
    arrowZL:TweenPosition(UDim2.new(0.5, -75, 0.08, -12), "Out", "Quart", 1.5)
end

function move()
    if openbool.Value == false and rip.Value == false then
        rip.Value = true
        firstZ:TweenPosition(UDim2.new(0.5, -350, 0.08, -50), "Out", "Quart", 2.5)
        secondZ:TweenPosition(UDim2.new(0.5, 250, 0.08, -50), "Out", "Quart", 2.5)
        arrowZR:TweenPosition(UDim2.new(0.5, 352, 0.08, -12), "Out", "Quart", 2.5)
        arrowZL:TweenPosition(UDim2.new(0.5, -375, 0.08, -12), "Out", "Quart", 2.5)
        repeat
            wait()
            arrowZR.Rotation = arrowZR.Rotation + 2
            arrowZL.Rotation = arrowZL.Rotation - 2
        until arrowZR.Rotation == 180 and arrowZL.Rotation == 0
        rip.Value = false
        openbool.Value = true
    else if openbool.Value == true and rip.Value == false then
        rip.Value = true
        firstZ:TweenPosition(UDim2.new(0.5, -50, 0.08, -50), "Out", "Quart", 2.5)
        secondZ:TweenPosition(UDim2.new(0.5, -50, 0.08, -50), "Out", "Quart", 2.5)
        arrowZR:TweenPosition(UDim2.new(0.5, 52, 0.08, -12), "Out", "Quart", 2.5)
        arrowZL:TweenPosition(UDim2.new(0.5, -75, 0.08, -12), "Out", "Quart", 2.5)
        repeat
            wait()
            arrowZR.Rotation = arrowZR.Rotation - 2
            arrowZL.Rotation = arrowZL.Rotation + 2
        until arrowZR.Rotation == 0 and arrowZL.Rotation == 180
        rip.Value = false
        openbool.Value = false
    end
    end
end

load()

arrowZR.MouseButton1Click:connect(move)
arrowZL.MouseButton1Click:connect(move)