One of the reasons I think no human will ever be immortal is that we can't even make houses live for more than a couple of hundred years in the general case, and houses are objects rather than dynamic systems.
Human bodies are able to regenerate and repair themselves to a certain extend (no single cell in your body will live as long as you). In fact, one of the factors that diminishes our life is a malfunction of our regeneration processes: cancer.
Human body machinery mostly outperforms man-made machinery i.e. there is nor reason to believe that a human heart can beat for ever if we find a way to allow it to regenerate for ever without faults.
Human brains are able to perform medicine which is also a positive feedback loop for how long human bodies can last.
In a nutshell, a dynamic system has a least the chance to reverse or repair damage done to it due to entropy, a static one has not.
Unless you're a woman who dies before menopause...
Sure, if a building falls into disuse it may die, but is that not true of people too?