Why do our scripts only work for ourselves? (note: they are the same.)

so me and my friend are working on a game, yet for some reason, when I playtest it, only the animation buttons that I made work for myself. it's even worse in public servers, It doesn't work at all! please help. P.S the scripts for me and my friends animation-buttons are the same -pwgth

local animation = Instance.new("Animation")
animation.AnimationId = "rbxassetid://7284962336"

local trackanimation = nil
local playability = true

function playAnimation (animationSource)
    if playability == true then 
        local plr = game.Players.LocalPlayer
        trackanimation = plr.Character.Humanoid:LoadAnimation (animation)

        trackanimation.KeyframeReached:Connect(function()
            print("10!")

        end)
        trackanimation:play()
    end
end
script.Parent.MouseButton1Click:Connect(playAnimation)