Running Animation won't play

Hello, I am trying to make client to server replication for this running animation, but when I hold shift, it does not run.

Local script:

local UIS = game:GetService('UserInputService')
local Player = game.Players.LocalPlayer

UIS.InputBegan:Connect(function(input)
	if input.KeyCode == Enum.KeyCode.LeftShift then
		script:WaitForChild("RemoteEvent"):FireServer(Player, "true")
	end
end)

UIS.InputEnded:Connect(function(input)
	if input.KeyCode == Enum.KeyCode.LeftShift then
		script:WaitForChild("RemoteEvent"):FireServer(Player, "false")
	end
end)

Server scirpt:

script.Parent.OnServerEvent:Connect(function(plr, running)
	local track
	local humanoid
if running == "true" then
	if plr then
		local char = plr.Character or plr.CharacterAdded:Wait()
		if char then
			humanoid = char:WaitForChild("Humanoid")
			if humanoid then
				local animator
				local success, result = pcall(function()
					animator = humanoid:FindFirstChild("Animator")
				end)
				if not success then
					local Animator = Instance.new("Animator")
					Animator.Parent = humanoid
				end
				if humanoid:FindFirstChild("Animator") then
					animator = humanoid:FindFirstChild("Animator")
					local Animation = Instance.new("Animation")
					Animation.AnimationId = 'rbxassetid://9397141402'
					track = animator:LoadAnimation(Animation)
					track.Looped = true
						track:Play()
						humanoid.WalkSpeed = 35
				end
			end
		end
		end
	elseif running == "false" then
		track:Stop()
	humanoid.WalkSpeed = 16
end
end)

Explorer:
image

I’ve tried many solutions, they won’t work. Any ideas?

p.s: this local script is located in (StarterPlayer > StarterPlayerScripts