Why is the animation not playing?

So i have a script that is suppose to enable the player to slide, but the script is not playing the animation.

local Sliding = false

local WalkToSlide = Instance.new("Animation")
WalkToSlide.AnimationId = "rbxassetid://"..6467630387

local SlideLoopAnimaion = Instance.new("Animation")
SlideLoopAnimaion.AnimationId = "rbxassetid://"..6789330585

local WalkToSlideAnimationTrack = Animator:LoadAnimation(WalkToSlide)
local SlideLoopAnimationTrack = Animator:LoadAnimation(SlideLoopAnimaion)

--#Start sliding
local function Slide()
    if _Delay then return end

    Sliding = true
    --_Delay = true

    WalkToSlideAnimationTrack:Play()
    WalkToSlideAnimationTrack.Stopped:Connect(function() SlideLoopAnimaion:Play() end)
end

--#Stop sliding
local function StopSlide()
    if Sliding then return end
    if not _Delay then return end

    Sliding = false

    if WalkToSlideAnimationTrack:IsPlaying() then WalkToSlideAnimationTrack:Stop() else SlideLoopAnimaion:Stop(0.1) end
end

uis.InputBegan:Connect(function(Key)
    if Key.KeyCode == Enum.KeyCode.LeftShift then Slide() end 
end)

uis.InputEnded:Connect(function(Key)
    if Key.KeyCode == Enum.KeyCode.LeftShift then StopSlide() end
end)

I made a script in the past which worked but for some reason this script and the older script no longer works. The script is located in StarterPlayer -> StarterPlayerScript.