Why does this error pop up?

What does ScreenGui is not a valid member of PlayerGui mean when you put ScreenGui in StarterGui?

function timer(timecountdown)
	local timerValue = timecountdown
while timerValue ~= 0 do
	wait(1)
	timerValue = timerValue - 1
	for i, v in   pairs(game.Players:GetChildren()) do
		v.PlayerGui.ScreenGui.TextLabel.Text = timerValue
	end
end
end

function timerhide(timecountdownhide)
	local timerValuehide = timecountdownhide
while timerValuehide ~= 0 do
	wait(1)
	timerValuehide = timerValuehide - 1
	for i, v in pairs(game.Players:GetChildren()) do
		v.PlayerGui.ScreenGui.TextLabel.Text = "Time Left To Hide: " .. timerValuehide
	end
end
end

function timeri(timei)
	local timerValuei = timei
while timerValuei ~= 0 do
	wait(1)
	timerValuei = timerValuei - 1
	for i, v in pairs(game.Players:GetChildren()) do
		v.PlayerGui.ScreenGui.TextLabel.Text = "Intermission: " .. timerValuei
	end
end

end

while true do 
	print("23")
	for i, v in   pairs(game.Players:GetChildren()) do
		if v.Character.Torso.Material == Enum.Material.Plastic then
			game.Workspace.Jackel.SurfaceGui.TextLabel.Text = v.Name .. ", "
			v.leaderstats.sCoins.Value = v.leaderstats.sCoins.Value + 200
		end
		v:LoadCharacter()
	end
	
		timeri(10)	
	
	for i, v in  pairs(game.Players:GetChildren()) do
			v.PlayerGui.ScreenGui.TextLabel.Text = "Teleporting Players..."
	end
		


for i, v in   pairs(game.Players:GetChildren()) do  v.Character.Torso.CFrame = CFrame.new(Vector3.new(-126.7, 41.61, -141.1)) -- Change numbers to whatever	
wait(1)
v.PlayerGui.ScreenGui.TextLabel.Text = ""
wait(1)

end


timerhide(20)
for i, v in pairs(game.Players:GetChildren()) do 
v.PlayerGui.ScreenGui.TextLabel.Text = "The Illness Has Been Let Out!"
end

wait(1)
local iCopy = game.ServerStorage.DFDIllness:Clone()
iCopy.Parent = game.Workspace
iCopy:MakeJoints()
timer(90)

for i, v in pairs(game.Players:GetChildren()) do
v.PlayerGui.ScreenGui.TextLabel.Text = "Game Ended"

end
wait(1)
for i, v in pairs(game.Players:GetChildren()) do
	v.PlayerGui.ScreenGui.TextLabel.Text = "Teleporting Players Back..."
end
wait(1)




for i, v in   pairs(game.Players:GetChildren()) do  v.Character.Torso.CFrame = CFrame.new(Vector3.new(13.06, 68.92, -2.18)) -- Change numbers to whatever	
v.PlayerGui.ScreenGui.TextLabel.Text = ""

end


game.Workspace.DFDIllness:Destroy()

end