When you say "new", the Archos G9 80 is rather an old device, so is it really "new" or just new to you?
I assume you mean WiFi, so can it see networks but not connect, or just not see any networks? Does your router have some access control (such as a list of approved MAC addresses) which might be blocking it?
Please give us as much detail as you can: "it doesn't work" is hard to fix because there are so many possibilities.