Sorry, what is bbox? If it’s an NAS of some type, what exactly does the fact that you’ve changed internet service providers mean? Are you using their hardware as your router? Is there some possibility that this new router is creating more than on subnet, and the Sonos is on one side, and the bbox on the other?

Please, we need a lot more information if we’re to help. Otherwise you could just call Sonos Support directly to discuss it.

When you speak directly to the phone folks, they have tools at their disposal that will allow them to give you advice specific to your Sonos system and network.

It's an internet box by bouygues.

Do you have a support in french for a call ?

Is that a combined modem/router/switch? If so, did you first cable one Sonos device to the new router and power-cycle any other Sonos products, then add the new WiFi credentials via "Settings/System/Network/Manage Networks/Update Networks” .. As mentioned in this Sonos support article?

https://support.sonos.com/en-us/article/connect-sonos-to-a-new-router-or-wi-fi-network

Oh and when that’s complete, (if no longer needed), do not forget to remove your old WiFi network credentials too, as outlined in the link below:

https://support.sonos.com/en-us/article/remove-a-wifi-network-from-your-sonos-system

You should be able to reach the French support line at this link:

Sonos Support

Or you could possibly change your the SSID and password in the new router to your old SSID and password.

After a call to the french support my problem is solve.