Re: Lawyers... start your engines
But this is about the equipment "failing" because a part of it has stopped working. IN this case I think it's a "slam dunk" case as our US friends might call it.
Has the equipment ceased to function - either in whole or part ? Yes
Is that due to a fault ? Yes, it's because a certificate has expired and so the equipment can't make secure connections.
Was that fault present, or could it reasonably be believed to be present, at the time of sale ? Yes, the certificate was part of the software, and it would have been obvious to anyone that it would expire on [some date].
So unless the retailer can that at least one of those statements is not true then they are liable and will lose in court. But since all three of those would be a given for the issue being described, they don't stand a chance. It's a completely different situation to the likes of Revolv where the equipment still "functions", but can't do something because an external service has stopped.
But that's a different (though related) debate - there needs to be some guarantee over provision of such services for at least a set time.