What products are in your system? Are any wired to the network? Describe your network. Give model numbers.

Try: https://support.sonos.com/en-us/article/improve-your-sonos-products-wifi-connection

https://support.sonos.com/en-us/article/supported-wifi-modes-and-security-standards-for-sonos-products

Try disabling 5GHz on your router.  Sounds like your newer Sonos gear (or your phone) is switching frequencies and your router can’t handle that.

​@Dolphinsnot 

This process of what you and others have attempted with failed and/or partial results need not be all that difficult.

BTW….the phrase “new network and made all the system changes” (or variations of the same wording) covers a lot of ground. Does it mean you changed the hardware such as router and modem, switched to a mesh setup, added range extenders, changed ISP’s, moved to a new location or a combination of any of the aforementioned? Regardless of which you did...here’s the simplistic way to make any of the changes mentioned.

The main key to the process is to use the same SSID and Password . Here are steps to follow in order given:

1. Unplug all Sonos and any other WiFi dependent devices if possible
2. Configure or make whatever changes you need to your network
3. Make sure your device is updated and connects to the network *
4. Delete the Sonos app
5. Plug in all your Sonos and let them comeback **
6. Download the Sonos app
7. Open the Sonos app and select “Join an Existing System/Sonos”
8. If you used the same SSID and Password everything will connect ***
9. Don’t forget to plug-in your other WiFi dependent devices 

So...that’s for next time you make alterations of any kind to your network. However, the question remains “what changes did you make this time and/or process followed”

 * If installing a Mesh network make sure that NONE of the satellites/nodes have DHCP rights (i.e. the ability to assign IP Addresses). Only the MAIN router/node should have DHCP rights.

** The process may take several minutes so be patient 

 *** If not your network isn’t configured properly which means you may need outside assistance from someone more knowledgeable; or you can call Sonos Tech Support

I’d add one bit, some new routers don’t support older modes by default and some Sonos don’t support the newer modes. You need to make sure modes Sonos can work with are enabled.

https://support.sonos.com/en-us/article/supported-wifi-modes-and-security-standards-for-sonos-products

All Sonos speakers and components can connect to wireless routers or access points that support 802.11b/g WiFi over 2.4GHz. Additionally, all Sonos speakers and components can connect to WiFi networks that use WPA and WPA2 Personal security standards, as well as unsecured WiFi networks.

That is the bare minimum, the article lists what speaker supports which mode so you can pick optimal settings.