tweenservice:create failed because instance is null what is wrong?

I just started learning code and I wanted to make a tween. But I get a error it says tweenservice:create failed because instance is null how do I solve this?

local tweenService = game:GetService('TweenService')
local part = script.Parent

local tweeningInformation = TweenInfo.new(
    5,
    Enum.EasingStyle.Bounce, --easing style of tween
    Enum.EasingDirection.Out, --direction of the tween
    10,
    true,
    2
)


local partProperties = {
    Size = Vector3.new(20,20,20);
    Color = Color3.new(255, 0, 0);
    Transparency = 0.5  
}

local Tween = tweenService:Create(Doort,tweeningInformation,partProperties)

Tween:Play()