Why doesn't RemoveDefaultLoadingScreen() seem to work in my script?

I made a custom loading GUI that looks pretty neat, but my one problem is that the default loading screen stays. Here's a snippet of my code:

local PlayerGui = game.Players.LocalPlayer:WaitForChild("PlayerGui")
local introgui = script.Parent.IntroGui:Clone()
local frame = introgui:WaitForChild("Background")
local loadingbar = frame:WaitForChild("LoadingBar")
local progress = loadingbar:WaitForChild("Progress")
local loadingstatus = frame:WaitForChild("LoadingStatus")
local lightfightlabel = frame:WaitForChild("LightFightLabel")
local whiteleaflabel = frame:WaitForChild("WhiteleafLabel")

game.ReplicatedFirst:RemoveDefaultLoadingScreen()

I think I'm using the RemoveDefaultLoadingScreen function properly, so what's the problem? This is in a local script in ReplicatedFirst. Thanks in advance!

Did you assign a parent for the GUI such as the playergui?