Try moving up the security on the router in steps .
1) No security ... works as you found out.
2) Try WEP
3) Try WPA
4) Try WPA/WPA2
You might find WPA works but WPA/WPA2 doesn't.
Also check Archos site for firmware updates.
Hands-on: Samsung Galaxy S8 review
1995-2015: How technology has changed the world in 20 years
Samsung's beautifully designed Galaxy S8 makes for better VR experiences too
47 iPhone camera tips to help you take better photos
Synology invites you to visit them at Insomnia on 26th – 29th August. Book your tickets now and visit Synology.