message d'erreur en voulant rejoindre un serveur public

The server hasn't updated to the newest version yet, you can temporarily switch back to the version of the server by right clicking Eco in Steam -> Properties -> Betas -> Select 11.0.0.

Note that this will stop automatic updates until you set it back to "None".

I learned french in school, but it's been a long while - thankfully there is translators all around nowadays, but I won't annoy you with trying to write in french, no worries :)

And that's when school french shows! :) Feel free to translate it to them in french :)