If connection to the router - and therefore to the Internet - fails, most certainly the router uses the same IP as the switch, which has a default IP of 192.168.0.1. Make sure the switch's IP is different from your router's one. Except for a possible IP conflict in a 192.168.0.0 subnet, every Easy Smart Switch is plug-and-play in its default configuration. See the installation/user guides for how to connect to the switch to change its IP.

dayblox wrote

Oh it must be it ! What IP address should I change the switch to ? Anything from 192.168.0.2 to 192.168.0.254 I guess ?

Doesn't really matter, but make sure it's an otherwise unused IP (meaning no static IP used by other devices and also no IP from the DHCP pool if any).

It was indeed an IP conflict, thank you so much !

You're welcome, great that it works now.