Welcome @sebastien.wurtzer
Thanks for sharing the details!
From a test, it seems the server is refusing to connect right now. The server has been very busy the last few days and that is likely a factor. I can connect with the lftp command line instructions but am unable to actually execute any commands or to move a file. So, the server is “there” just unable to respond in a timely way.
I see some unexpected statistics starting to show up at https://stats.galaxyproject.eu/, so let’s give the administrators a chance to review in their morning and see if things improve.
I’ll be posting updates to Galaxy Europe – jobs stuck in "new" state - #4 by jennaj first but please do ping me again here if FTP is still not working in the next 12 hours or so and we can follow up more. 
I’m glad you asked and hopefully this resolves soon!