Trying to make an animation, it won't play. Help? (Unanswered)

Hi, I'm trying to make my first animation for a game I'm working on. I'm having an issue with this animation where everything works fine, it prints 'done' but the animation will not play. I've uploaded to roblox and done everything the wiki says.

Here's the code -

local tool = script.Parent
local player = game.Players.LocalPlayer

local swing = Instance.new("Animation")
swing.AnimationId = "http://www.roblox.com/Asset?ID=273714865"

local animtrack = nil
local canplay = true

script.Parent.Equipped:connect(function(mouse)
mouse.Button1Down:connect(function(hitting)
if canplay == true then
    canplay = false
local playit = player.Character.Humanoid:LoadAnimation(swing)
playit:Play()

canplay = true
print 'done'
end
end)
end)