Why dose this Key function Not work as intended?

So I am making a 3rd Person shooter game, and I am making a button that is activated with the key "K" so when you press "K" a Gui frame pops so I tried making that in a local script inside StarterGui here's the script

game:GetService("UserInputService").InputBegan:Connect(function(key)
    if key.KeyCode == Enum.KeyCode.K then
        game.StarterGui.ShopGui.Frame.Visible = true-- Turns on frame
  end
end)

I can't figure why it won't work

The StarterGui is basically just a storage place for all the GUIs to be replicated to the client when they join the game and respawn. You want to reference the PlayerGui.

local Players = game:GetService("Players")
local LocalPlayer = Players.LocalPlayer

game:GetService("UserInputService").InputBegan:Connect(function(key)
    if key.KeyCode == Enum.KeyCode.K then
        LocalPlayer.PlayerGui.ShopGui.Frame.Visible = true-- Turns on frame
  end
end)

Make sure this is in a local script, as that is how you use the Input Service.

local player = game.Players.LocalPlayer

game:GetService("UserInputService").InputBegan:Connect(function(key)
    if key.KeyCode == Enum.KeyCode.K then
        player.PlayerGui.ShopGui.Frame.Visible = true-- Turns on frame
  end
end)

You shouldn't address the PlayerGui, as anything in that gets cloned into the player whenever they join. You always change GUIs in the player's PlayerGui.