@arepo
It seems you may have conflicts with your network
You should remove all Ethernet connections, the switch and the Boost and go with your WiFi as the primary source to link you Sonos.
Also make sure that the ATT router side of the box is set to Bridge mode.
To accomplish the above you must: *
- Unplug all Sonos
- Remove the Ethernet cables, switch and Boost **
- Unplug your Linksys 6E
- Verify that the ATT router portion of the box is set to Bridge mode (you may have to contact your ISP)
- Connect your Linksys 6E to the ATT modem via Ethernet and plug it in
- If necessary be sure to use the same SSID and Password as before to setup the Linksys 6E
- Connect you device and verify that you have Wi-Fi and Internet connection
- Delete the Sonos app from your device
- Plug-in your Sonos (not the sub) and let them all come back
- Re-install the Sonos App
- Select “Join and Existing System”
- Follow and accept all prompts
- Sign-in with your credentials
- After all Sonos is back on-line Factory Reset the Sub
- In the App select Add a Product to get the sub back into your system
- Add the sub to the Arc
* If you don’t feel comfortable doing the following call Sonos Tech Support to let them walk you through the process.
** You will no longer use/need any of these products
Together Everyone Achieves More = T.E.A.M.