Here's the thing about Sonos: most "not working" problems are the network, not the speaker. The speaker is usually fine — your phone's app just can't reach it. So start with one reboot that clears a lot of cases, then match your exact symptom to its fix.
Do this first — reboot everything
Unplug each Sonos speaker for at least 30 seconds, plug back in, and reboot your router too. Wait for the rooms to reappear in the app before testing. A stale network state is behind a surprising share of Sonos trouble, and this clears it. While you're at it, make sure your phone is on the main 2.4 GHz Wi-Fi (not a guest network or VPN) — Sonos discovery needs that.
Then match your symptom
A room is missing from the app, or it says "no products found" That's a discovery/network problem — the app can't see the speaker. See Sonos not finding speakers for the multicast/IP-reservation steps and the Ethernet-to-SonosNet workaround.
A speaker is flashing red (or orange) The light is telling you something specific. Why is my Sonos flashing red decodes it — and corrects the common myths (red is setup/error; orange is overheating; green is mute).
You're getting a connection error code (1001, 1101, etc.) Those are network-reachability errors, not hardware. Sonos error 1001 walks the fix (same 2.4 GHz network, clear VPN/ad-blockers, wired setup).
Alexa or voice isn't responding Usually the mic is muted. See why is my Sonos Alexa not working.
No TV sound (soundbar) That's HDMI ARC/eARC, not Wi-Fi — a different chain entirely. See Sonos not connecting to TV.
The one rule that saves time
Don't reach for Bluetooth. Sonos uses Wi-Fi (and its own SonosNet) for whole-home audio — not Bluetooth (the portables only use Bluetooth for direct phone streaming). If your system isn't playing or the app can't find it, the fix is on the Wi-Fi/network side, not Bluetooth.
FAQ
What's the one fix that helps most? A reboot — unplug each speaker for 30+ seconds and reboot the router, with your phone on the main 2.4 GHz network. It clears the largest share of issues.
The speaker plays but the app can't control it. That's a discovery/network problem. Reboot, match the network, and reserve the speaker's IP — see the "not finding speakers" guide.
Is my speaker broken? Rarely. The vast majority of Sonos "not working" cases are network/app, and the speaker is fine once it's reachable again.
Why won't Bluetooth fix it? Sonos doesn't use Bluetooth for grouping or setup — it's Wi-Fi-based. The fix is the network, not Bluetooth.