DataStore wont work properly?

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

local dataStore = game:GetService("DataStoreService"):GetDataStore("CoinStorage")

local function autoSave()
	-- this is a much safer way of saving
	-- btw this checks if the player count is above 0
	if #Players:GetPlayers() > 0 then
		for _, player in next, Players:GetPlayers() do
			dataStore:SetAsync(player.UserId, 			player:WaitForChild("leaderstats"):WaitForChild("Coins").Value)
		end
	end
	
	wait(120) -- go to roblox wiki and change it according to the times shown on that page
	autoSave()
end

-- wraps the call of autosave in a function so it doesn't go for more then twice amounts of time
local recursiveCall = coroutine.wrap(autoSave)
recursiveCall()

-- run this event only once, not twice
Players.PlayerAdded:Connect(function(player)
	local stats = Instance.new("Folder", player)
	stats.Name = "leaderstats"
	-- changed it to a number value so if you are using decimals the value can still be usable
	local coins = Instance.new("NumberValue", stats)
	coins.Name = "Coins"
	coins.Value = dataStore:GetAsync(player.UserId) or 0
	
	--[[ I took out your changed event due to that being easily exploited to hackers. They can just change the value of their coins,
	and there it goes, it saves right there. Also if the "coins" value is changing rapidly, the connection to the data store wiil be
	throtlled at some point, and that's another reason why I took that out as well. --]]
end)

Players.PlayerRemoving:Connect(function(player)
	dataStore:SetAsync(player.UserId, player:WaitForChild("leaderstats"):WaitForChild("Coins").Value)
end)

I suggest changing the name of the Data Store as well. If you have a second script for this, delete it. If you have more questions about it, make it one or comment on this.