Please can somebody fix this code, the data store is not saving the cash the player makes?

your code actually looks great, the problem might actually be with when the data is retrieved.. you see, the when you retrieve data but that data hasn't yet been set, the function won't error, it will instead return nil.. and looking at your code, this would logically interpret to cash.Value = nil for the first time the a key is used, which will cause unpredictable behavior - from halting, etc..

so here's how you should do it:

local Players = game:GetService("Players");
local DataStoreService = game:GetService("DataStoreService");

local Datastore = DataStoreService:GetDataStore("MyDataStore");

Players.PlayerAdded:Connect(function(player)
	local leaderstats = Instance.new("Folder", player);
	leaderstats.Name  - "leaderstats";

	local cash = instance.new("IntValue", leaderstats);
	cash.Name =  "Cash";

	local data = nil;

	local s, e = pcall(function()
		data = Datastore:GetAsync(player.UserId.."-cash")
	end)

	if(s) then
		print("data successfully loaded")'
		data = data or 0 --this is most important; if no data has been saved, replaces it with 0 for default
		cash.Value  = data
	else
		warn("There was a problem loading data:", e);
	end
end);


Players.PlayerRemoving:Connect(function(player)
	local leaderstats = player.leaderstats
	local cash = leaderstats.Cash

	local s, e = pcall(function()
		Datastore:SetAsync(player.UserId.."-cash", cash.Value)
	end);

	if(s) then
		print("data successfully saved");
	else
		warn("There was a problem saving data:", e);
	end
end)