Script in ServerScriptService:
wait(5)
game.Players.PlayerAdded:Connect(function()
if game.Players.LocalPlayer.hasJoined.Value == false then
game.Players.LocalPlayer.hasJoined.Value = true
end
end)
Script in LocalScript in StarterGui:
local joinedVal = game:GetService("Players").LocalPlayer.hasJoined
if joinedVal.Value == false then
script.Parent.MainUI.StarterPack.Visible = true
elseif
joinedVal.Value == true then
script.Parent.MainUI.StarterPack.Visible = false
end

1 comment
LocalPlayer is nil to the server.