Script in ServerScriptStorage fires errors when playing in-game, but works in Studio?

I have a script, remotefunction, etc. that open a shop when you right click on a part, that works perfectly in studio, but I always get the same errors in-game! Could someone please assist me?

The error I get in-game: https://gyazo.com/c152f5a990f8826a43c92aa69846ce8b

What it should look like when I buy it: https://gyazo.com/0a29e9f208e8e2d37e877904ebfef2db

The code basically opens the menu when the remoteevent is fired and IS STORED IN SERVERSCRIPTSTORAGE

This is the code that is getting the error:

local open= game.ReplicatedStorage.menuEvent
open.OnServerEvent:connect(function(plr, id)
    repeat wait() until plr.PlayerGui.Main~= nil
    plr.PlayerGui.Main.Frame.Value.Value=id 
    plr.PlayerGui.Main.Frame.Visible=true
end)

Client sided (fires the event):

children=workspace.Planets:GetChildren()
for i=1, #children do
children[i].detect.ClickDetector.RightMouseClick:connect(function()
    print"db"
    game.ReplicatedStorage.menuEvent:FireServer(children[i].Name)
    print"debug"
end)
end

Please help!