UnknownHostException means your WFA is not aware of this hostname that you have provided. Its possible causes are the WFA server and your host belonging to different domains or your DNS not configured properly.
To get out of this error, provide the IP Addess of this host instead of the hostname.
If you want to use the hostname itself, you can add this host and the corresponging IP into etc/hosts file.
If this post resolved your issue, help others by selecting ACCEPT AS SOLUTION or adding a KUDO.
thank you for your answer, I finially end up uninstalling completely the previous version and reinstalling from scrach, to make it work I had to follow the steps on the wfa page and that works. Now I am facing issues making with some packs.