The helpfroum is customer to customer support only, you will not get a comment from Sky here as they do not reply or respond to posts.
Also, there are already many other threads on this topic. Sky only had licencing to show the Walking Dead box sets (series 1-5) until 31st October, that is why they are no longer available. Series 6 is only available as Catch Up, so each episode expires separately.
The other series may (and most likely will) return some time in the future, but no-one can say for certain when that will be.