?Data Store Wont Work in player

There are a few things that you need to change. Firstly, there is no reason to save their stats every time they change. That will cause your server lots of issues.Secondly, SetAsync and GetAsync have a string as their first parameter, not a number(int). Also, you must take account for when the server is closing and the Player Removing event is not fired (This happens when last person leaves the server, or when it is shutdown or crashed for whatever reason.) Taking all that into account, your code should be changed to this:

local DataStore = game:GetService("DataStoreService")
local ds = DataStore:GetDataStore("CreditSaveSystem")

game.Players.PlayerAdded:Connect(function(player) -- Connect, not connect
    local Credits = Instance.new("IntValue",player)
    Credits.Name = "Credits"
    Credits.Value = ds:GetAsync('Player:'..player.UserId) or 0 -- string parameter 
end)


game.Players.PlayerRemoving:Connect(function(player)
    ds:SetAsync('Player:'..player.UserId, player.Credits.Value)
end)
game:BindToClose(function() -- if the last player in the game leaves, don't close the server down until it's saved
	for a,player in pairs (game.Players:GetPlayers()) do
		ds:SetAsync('Player:'..player.UserId, player.Credits.Value)
	end
end)