Why when you collect this cash block it does not give you cash?

Problem:

If you want to use Filtering Enabled and manipulate a player's stats it is best you do it with a Remote Event. Simply doing it, which I assume you are doing it in, a Local Script will only change the player's values on the client side not the server side.

Solution:

Like I mentioned above I would use a Local Script to register the Touched event of the part and can manipulate the Player's Gui, but use a Remote Event to actually manipulate the Player's Stats. Now when I reference in a variable to the Remote Event you can change the reference to it in the hierarchy of the game as you please. In general it would look something like this with a Local Script and a "Listener" script.

Code:

Local Script:

script.Parent.Transparency = 0
script.Parent.CanCollide = true
local remote = game.ReplicatedStorage:WaitForChild("RemoveEvent")
script.Parent.Touched:Connect(function(onTouched)
	local go = true --I am making a debounce so the Remote Event is not fired too many times as when you touch a part you touch it more than once.
	if go == true then 
		go = false
		script.Parent.Transparency = 1
		script.Parent.CanCollide = false
		game.Players.LocalPlayer.PlayerGui:WaitForChild("Essentials"):WaitForChild("Prize").Visible = true --Added :WaitForChild() so no errors because of it not being there
		game.Players.LocalPlayer.PlayerGui.Essentials.Prize.Text = 'You have collected 3 Tokens!'
		remote:FireServer()
		script.Parent.Transparency = 0
		script.Parent.CanCollide = true
		game.Players.LocalPlayer.PlayerGui:WaitForChild("Essentials"):WaitForChild("Prize").Visible = false --I'd assume you  want that set to false to make it invisible after?
		wait(2)
		go = true
	end
end)

Server Script(AKA "Listener Script"):

local remote = game.ReplicatedStorage:WaitForChild("RemoveEvent")


remote.OnServerEvent:Connect(function(plr)--First parameter will always be the player who fired the event
	plr:WaitForChild("leaderstats"):WaitForChild("Tokens").Value = plr:WaitForChild("leaderstats"):WaitForChild("Tokens").Value + 3 --Again I added :WaitForChild() for same reason
end)

If you have any problems you can comment on my answer and I would be glad to help. If this helped you then don't forget to accept my answer. Also note that you can put the "Listener Script" where you want, but not ServerScriptService or ServerStorage as these areas are for the server side only and not the client really. But you get my point. It should also be considered to name your RemoteEvent so that the "Listener Script" listens to the right Remove Event.