One of our domains is blocked by URL:Blacklist / please unlist it asap

Hello, our clients use our platform to set up websites for their events. One of them is refashionday.fr; it is totally legit, and is for some reason blocked by Avast, reason given is URL:Blacklist.
Can you please assist in unlisting this domain asap from the blacklist and give the reasons that lead to this problem.
Many thanks,

https://forum.avast.com/index.php?topic=14433.msg1289438#msg1289438