GUI's don't work in FilteringEnabled for some reason?

Yeah and it says this error: GameGUI is not a valid member of PlayerGui in the dev console

But it works in studio and even if i get an explorer GUI and go to a server GameGUI is valid

I know it has to do with Filtering Enabled because that stuff worked in Experimental Mode well on another game I'm pretty sure, so how am I supposed to use PlayerGui!!!

I even tried WaitForChild() but it just added 2 infininte yeilds

-- hax noob
-- Times
intermissiontime = 35
roundIsPlaying = script.roundIsPlaying
-- End of Times
enabled = false
while true do
	wait(3)
	-- Intermission
	print("Intermission")
	for i,v in pairs(game.Players:GetChildren()) do
		print(v.Name)
		local char = v.Character
		local root = char.HumanoidRootPart -- Root part for teleportation
		root.CFrame = CFrame.new(workspace.Spawn.Position)
		local gui = v.PlayerGui
		local gamegui = gui.GameGui.GameFrame
		gamegui.Data.Text = "Intermission | Get Ready!" -- Nothing works here
	end
	-- Round
	wait(intermissiontime)
	enabled = true
	print("Round Started")
	roundIsPlaying.Value = true
	for i,v in pairs(game.Players:GetChildren()) do
		local char = v.Character
		local root = char.HumanoidRootPart
		root.CFrame = CFrame.new(workspace.roundpart.Position)
		local gui = v.PlayerGui
		local gamegui = gui.GameGui.GameFrame
		gamegui.Data.Text = "Round In Progress | Survive The Zombies!" -- And here
		
	end
	-- Zombies spawn below
	function SpawnZombie()
		game.ServerStorage["Zombie"]:Clone().Parent = workspace
	end
	while roundIsPlaying.Value == true do
		wait(2.5)
		SpawnZombie()
	end
	for i,v in pairs(workspace:GetChildren()) do -- Cleanup
		if v.Name == "Zombie" then
			v:Destroy()
		end
	end
end