RemoteEvent firing and received, but the script isn't working?

The RemoteEvent fires and is received as it's prints it, but the PlayerGui parts do not work, as well as the CameraFix cloning into the Player's character.

train = game.ReplicatedStorage.C153
Camera = workspace.CurrentCamera


game.ReplicatedStorage.C153Spawn.OnServerEvent:connect(function(player)
	print("Event Received")
		player.PlayerGui.MainMenuGui.Screen.DriveFrame.Visible = false
		player.PlayerGui.MainMenuGui.Screen.Spawning.Visible = true
		player.PlayerGui.MainMenuGui.Screen.Spawning.Text = "Spawning..."
		wait(0.01)
		local clone = train:Clone()
		clone.Parent = workspace
		clone:MakeJoints()
		clone.Bogies.SD_Bogie:MakeJoints()
		clone.Bogies.SD_Bogie2:MakeJoints()
		wait(1)
		player.Character.HumanoidRootPart.CFrame = CFrame.new(-2449.474, 10.174, -198.335)
		player.PlayerGui.MainMenuGui.Screen.Spawning.Visible = false
		player.PlayerGui.MainMenuGui.Screen.IntroMusic:stop()
  script.Parent.CameraFix:clone().Parent = player.Character
end)

This is what is visible in the developer console: https://gyazo.com/80f97bddbd4561a789993d930de82abb

If your game is Fe, the server can't see the descendants of PlayerGui, so you're going to make a client-handled RemoteEvent for GUI manipulating.

Also, the camera is client-sided only

--Local script
wait()
local player = game.Players.LocalPlayer
local GuiStuff = game.ReplicatedStorage.GuiStuff

GuiStuff.OnClientEvent:Connect(function(bool)
        if bool then
               player.PlayerGui.MainMenuGui.Screen.DriveFrame.Visible = false
               player.PlayerGui.MainMenuGui.Screen.Spawning.Visible = true
               player.PlayerGui.MainMenuGui.Screen.Spawning.Text = 'Spawning'
        else
               player.PlayerGui.MainMenuGui.Screen.Spawning.Visible = false
               player.PlayerGui.MainMenuGui.Screen.IntroMusic:Stop()
        end
end)

--Server code
local train = game.ReplicatedStorage.C153
local GUI = game.ReplicatedStorage.GuiStuff

game.ReplicatedStorage.C153Spawn.OnServerEvent:Connect(function(player)
        GUI:FireClient(player, true)
        wait()
        local clone = train:Clone()
        clone.Parent = workspace
        clone:MakeJoints()
        clone.Bogies.SD_Bogie:MakeJoints()
        clone.Bogies.SD_Bogie2:MakeJoints()
        wait(1)
        player.Character.HumanoidRootPart.CFrame = CFrame.new(-2449.474, 10.174, -198.335)
       GUI:FireClient(player, false)
       script.Parent.CameraFix:Clone().Parent = player.Character
end)