Data not saving if two players are in-game

Help and Feedback Scripting Support
2

You are checking is 1 player is in the game:

check = function()
	if #PlayersService:GetPlayers() == 1 then
		return false
	else
		return true
	end
end

You have a condition for true but you don’t have a condition for false:

PlayersService.PlayerRemoving:Connect(function(player)
	if check() == true then
		
		
		local UUID = player.UserId
		local success, err = pcall(function()
			SaveData(player)
		end)

		if success then
			LivePlayerData[UUID] = nil
			warn("DATA SAVED!")
		else
			LivePlayerData[UUID] = nil
			print(err)
			-- run function to attempt another save, the data is saved to a temporary "failed save" table to protect the data from simply being thrown away once the player leaves.
			warn("DATA DID NOT SAVE!")
		end
		
		
	end
end)