If you’ve factory reset it, you can only try going through the setup as though it is a new product. If you were wireless, the wifi in it may have failed in which case try it plugged into your router with Ethernet cable. If that fails, speak to Sonos support. 

Hello everyone my problem is:

The playbar my room does not appear in my sonos system — although it did set up properly with no error message— So, when I enter my room and open the Sonos app, a message that no products found “go to system settings” appears; I then go to system settings, scroll down and a window of Sonos system found in my wifi appears, so I click on “join the system nearby” — my system in the other rooms; an then my playbar appears in my system but none of the other speakers in the other rooms…

I already unplugged and plugged back in the router

Uodated each and every one of my products

Deleted an downloaded again the app

Reseted and installed back the playbar more than 5 times

What do you think I am doing wrong? 

It sounds like when you did a factory reset (usually not a good idea) you created a new system for it, rather than adding to existing. Hence you see it when your app joins one system and your other speakers when you join nearby system. 
 

If so, you need to factory reset it again, then go through installation again being sure to add to existing system.