Has your Bridge been added to your system/account?

Hello, my system does not find it. I use the new sonos app and it seems it's not working with it.

The Bridge is only compatible with the S1 app. You will have to download the Sonos S1 app and create a new system with the Bridge. It should show up on your account with the Upgrade Program discount once you do this.

Here’s more information about which Sonos products are compatible with the S2 app:
https://support.sonos.com/s/article/4786?language=en_US

I reset the bridge. I installed Sonos S1.

Led is flashing green on bridge.

But the app still can't find it :/

Is it wired via Ethernet into your network?

Is the Bridge directly connected to your router with an ethernet cable?

Yes

Yes RJ45.

Try rebooting your router.

I just succeed ! I had to choose the option "set UP sonos boost first" and then it recognise my bridge. 

Thank you!

Note that according to the terms of the trade-up program, the BRIDGE can only be traded up to the BOOST. 

On the other hand, the BOOST is a much better device than the original BRIDGE was, IMHO. Faster transmission speed, better interference rejection, and a better power supply (something that at this point seems to be a frequent failure point for the ancient BRIDGE).  It’s a worthwhile upgrade, and the BOOST can run either S1 or S2, although not both simultaneously.