Unsafe website blocked
Access has been blocked as the threat Mal / htmlgen-A was found on this website.
sophos web protection
Googling for "Mal/HTMLGen-A" shows that in the past many sites have been flagged by Sophos in error (even google and amazon). Also the instructions for removal I found were all for Windows, but the site runs Linux.
So I'm pretty sure this is a false positive.
Maybe in the past, anyway today in all site I browse I only find this on suspect site or site using suspect scripts, even if the web prot is not perfect, sophos is in the top av list with kaspersky, not like avast norton and co, and is a business solution so its probable your site is not accessible to sophos users becauuse sophos is often protected to not be disabled. You rather have to find which script causes this and kick it off your site, or try get in touch with a sophos tech so you can get clues because can also be a true fals positive to fix on their side