My walingg sound script has broken out of no where and I dont know why. Could anyone help?

So I have a script that changes the sound of your walking. It has been working just fine until like yesterday and it just broke out of nowhere and i dont know why. Help would be appreciated. And in case you're wondering what happened to it, it just doesnt play the sound anymore. All it does is plays the original roblox walking sound

local char = script.Parent
delay (0, function()
    while wait()do
        if char.Humanoid.FloorMaterial == Enum.Material.Marble then 
            char.Head.Running.SoundId = "rbxassetid://4231349974"
            char.Head.Running.Volume = 1
        end
    end 
end)