"Any reasonable person would assume that the antivirus would provide some protection to their computer even after the expiry date."
Really? I wouldn't be making any such assumption.
I ran Norton for quite a few years and distinctly recall receiving several warnings from about two months prior to expiry that renewal was needed before XXXX date. Are you saying you received no such warnings?
Even if you didn't, obviously you were aware of when your contract with Norton expired.
Norton isn't your mother. As already said, it sold you a licence to use its product for a finite period. If you haven't renewed the deal by that time I can't see why you would think they have any obligation to you at all.
