Is the game not recognizing RightShoulder?

local enabled = true
Player = script.Parent.Parent
character = Player.CharacterAdded:wait();
mouse = Player:GetMouse()

function onKeyDown(key)
key = key:lower()
if key == "x" then
RightShoulder = Player.Character.Torso["Right Shoulder"]
Run = game:GetService("RunService")
for i = 1,10 do
    RightShoulder.C0 = RightShoulder.C0 *CFrame.Angles(0, 0, 0.16)
    wait(5)
end 
    game.GetService("Chat"):Chat(Player.Character.Head, "First comes ROCK!")    
   end
end


mouse.KeyDown:connect(onKeyDown)

The Arm won't even move can someone help?