First of all it’s best to check that your local network and mobile Sonos controller device meets the current system requirements (See below links):

https://support.sonos.com/s/article/126

https://support.sonos.com/s/article/4875

I will guess you were previously using the Sonos S1 App as you have mentioned a Sonos Bridge in your system.

You might however find it best these days to set that now ‘old’ Bridge aside and just cable the Sonos Boost to your main router instead and power on each device one at a time, perhaps start with just the Boost and one of your Play:3’s and see if the speaker appears in the S1 App. If it appears, then immediately check for updates and see if the two devices (Boost & Play:3) will update their firmware, but resist any update offered to an S2 system at this stage.

If you have problems you could also try ‘daisy chaining’ the Play:3 and cable that to your Boost and then see if that updates… bear in mind to stay away from the S2 update as that may complicate the issue for you at this time. If the devices just won’t update at this stage, then you will likely need to contact Sonos Customer Support via this LINK and seek their assistance.

Assuming the Play:3 works and it’s firmware is updated to the latest S1 release, then go onto do the same steps with your other Sonos products and get them all appearing in the S1 App and updated.

Next, its a case of trying to establish if your Sonos Connect:Amp is capable of running on an S2 system. If it is, you can go onto update all your devices to an S2 system.

The easiest way to find out the information you need here, is to check your online Sonos profile. Go here: 

https://www.sonos.com/myaccount/system/households/devices/

See what is mentioned next to the Connect:Amp if it is S2 compatible, or not?

Whatever you do, do not update your system to S2, unless you fully intend to either ‘split’ your system into S1/S2, or you are happy that the Amp is S2 compatible. Otherwise you may perhaps prefer to stick just with an S1 system only, so that your devices can continue to work with each other.

You can find more information about S1/S2 setups in this link below… just read through the S1/S2 topics to get a better understanding of the possible implications of upgrading to S2.

S1/S2 INFORMATION

Anyhow all being well, you should hopefully get your system up and running on S1 at the very least.

Just to further assist you can get the S1 controller App here to get you started.. just scroll past the S2 App section to the latest S1 controller download links:

https://support.sonos.com/s/downloads

Hope that information assists to get your Sonos products back up and running.

Thank you so much Ken.  It worked !!

i really appreciate your help