Why do I only see this frame in roblox studio but not when I play the game?

It's the same confusion I have when I was starting so I'll explain you

The function of the StarterGui is to copy itself into the Player's Gui when the game loads

So the real Gui is not in StarterGui it is in Player.PlayerGui

First: The gui can only be changed with a local script

Second: The local script has "LocalPlayer" to refers to your player

Create a local script in StarterGui or StarterPlayerScripts and put

inviswall = workspace.Hall.InvisWall
Player = game.Players.LocalPlayer --This is your player
PlayerGui = Player:WaitForChild("PlayerGui") --This is your local Gui I used WaitForChild because the Gui takes time to load
ScreenGui = PlayerGui:WaitForChild("ScreenGui") --Same here
blindness = ScreenGui:WaitForChild("Blindness") --And here


function ShowWall()
    print("Touched")
    inviswallTransparency = 0
    print("Wall visible.")
    wait(5)
    blindness.BackgroundTransparency = 0
    wait(5)
    print("Unblinding.")
    for i = 0, 1, 0.1 do
        blindness.BackgroundTransparency = i
    end
end)

workspace.Hall.InvisTouch.Touched:Connect(ShowWall)

You can also put your local script inside ScreenGui in StarterGui and it will work because the script will also be copied and runned inside the player gui so u can use script.Parent to refer to the ScreenGui and script.Parent.Blindness for the Blindness Frame

Sorry for my english hope you understand me