I encounter the same issue that mentions in the following post.
Although the link that the Sophos helpdesk mention no longer contains the update installer for Linux as mentioned in this original posting. Wondering if this is still available for Linux? Or is there a newer Linux (free) version that is available
on top of the Conversations list in Free Tools is the retirement notification for sav9. And right below your post is another one about this failed download. Wonder why you missed these as you've found the older thread you're referring to.