Animation won't play

the animation won’t play there are no error messages either

local cam = workspace.Camera
local current_cam = workspace.CurrentCamera
local arms = game:GetService("ReplicatedFirst"):WaitForChild("arms"):Clone()
local plr = game.Players.LocalPlayer
local userinputservice = game:GetService("UserInputService")
local runservice = game:GetService("RunService")
local sprint_speed = 40
local defult_speed = 16
local animation_track
arms.Parent = cam
userinputservice.InputBegan:Connect(function(input, isTyping)
	if isTyping then return end
	if input.KeyCode == Enum.KeyCode.LeftShift then
		local chr = plr.Character or plr.CharacterAdded:Wait()
		local humanoid = chr:WaitForChild("Humanoid")
		humanoid.WalkSpeed = sprint_speed
		local animation = arms.run
		local animator = arms.Humanoid
		if not animation_track then
			animation_track = animator:LoadAnimation(animation)
		end
		animation_track.Looped = true
		print(animation_track.IsPlaying)
		print(animation_track)
		--if not animation_track.IsPlaying then
		--	print("not playing")
		--	animation_track:Play()
		--end
		--animation_track:AdjustSpeed(1.5)
		animation_track:Play()
	end
end)
runservice.RenderStepped:Connect(function()
	arms:SetPrimaryPartCFrame(cam.CFrame * CFrame.new(0, -2, -1))
end)

userinputservice.InputEnded:Connect(function(input, isTyping)
	if isTyping then return end
	if input.KeyCode == Enum.KeyCode.LeftShift then
		local chr = plr.Character or plr.CharacterAdded:Wait()
		local humanoid = chr:WaitForChild("Humanoid")
		humanoid.WalkSpeed = defult_speed
		--if animation_track then
		--	animation_track:AdjustSpeed(0)
		--	print(animation_track.IsPlaying)
		--	print(animation_track)
		--end
		animation_track:Stop()
	end
	
end)