My code is a brick that you touch to open a gui then you touch another to close it?

Sorry for the weird title, if you want a quick TL:DR on this it is about:

18:36:38.974 - FireClient: player argument must be a Player object

I would really appreciate some help here

Okay so I have a brick:

"RemoveGui" and inside there there is a script

local brick = script.Parent
brickClosedEvent = game.ReplicatedStorage.Event.BrickClose
local debounce = false

brick.Touched:Connect(function(hit)
	if not debounce then
		debounce = true
		print("activated")
		local player = game.Players:GetPlayerFromCharacter(hit.Parent)
		brickClosedEvent:FireClient(player)
		print("WorkingClose")
		wait(0.5)
		debounce = false
	end
end)

And I have another brick called "AddGui" which will show the gui, whereas RemoveGui will close it whcih goes

local brick = script.Parent
brickTouchedEvent = game.ReplicatedStorage.Event.BrickTouched
local debounce = false

brick.Touched:Connect(function(hit)
	if not debounce then
		debounce = true
		local player = game.Players:GetPlayerFromCharacter(hit.Parent)
		brickTouchedEvent:FireClient(player)
		print("Working")
		wait(0.5)
		debounce = false
	end
end)

And then in replicated storage I have a folder called "Event" and inside that two remote events which are called "BrickClose" and "BrickTouched"

And finally in StarterGui I have got a local script called "BrickGui" which has a Gui called "Gui" and a frame inside that called "Frame".

So the local script (BrickGui) goes:

local gui = script.Gui
local brickTouchedEvent = game.ReplicatedStorage.Event.BrickTouched
local brickCloseEvent = game.ReplicatedStorage.Event.BrickClose


brickTouchedEvent.OnClientEvent:Connect(function()
	gui.Enabled = true
	print("open")
end)

brickCloseEvent.OnClientEvent:Connect(function()
	print("going to close")
	gui.Enabled = false
end)

So what I am aiming for is that the two remote events will fire and the local gui will pick them up and do so accordingly.

However

What my problem is that when I touch AddGui it says, "18:36:38.974 - FireClient: player argument must be a Player object"

I have read other articles on this but I can't really grasp what I should do.

I would really appreciate some help here, Thanks

What you're doing wrong inside your script is that you're not checking if the part that's touching it is a child of the character.

Here's how u can check that :

brick.Touched:Connect(function(hit)
    if hit.Parent:FindFirstChild('Humanoid') and not debounce then
        debounce = true
        local player = game.Players:GetPlayerFromCharacter(hit.Parent)
        brickTouchedEvent:FireClient(player)
        print("Working")
        wait(0.5)
        debounce = false
    end
end)

You can make the gui visible/invisible not removing or creating.That might fix your problem