I hated my AT&T modem’s wifi router, I ended up with a ‘real’ router connected to its WAN port, years ago. AT&T just didn’t want to give me the control I wanted/needed to have. Bean counters, I assume. But that was many years ago, I currently use T-Mobile’s 5G router with no issues (although I can’t assign IP addresses, which I want to…but still haven’t had the need to).
It seems odd that it won’t connect via Ethernet cable, it does suggest some sort of port blocking software, such as a VPN or virus protection. Have you called Sonos Support to discuss it?
When you speak directly to the Support staff, they have tools at their disposal that will allow them to give you advice specific to your network and Sonos system.
Most likely you changed SSID and Password.
Two (2) Key factors when changing ISP’s or routers is to:
- Unplug all Sonos
- Use same SSID and Password when setting up your new router/ISP
After all is setup and your device with the Sonos app is connected to WiFi:
- Delete the Sonos app for your device
- Plug in all Sonos and let them come back (this may take a few minutes)
- Reinstall the Sonos app on your device
- Select Join an existing system