speakers offline?

What speaker? When does it say this? Using a voice command like Google or Alexa? Can you elaborate?

At a guess: because it’s offline? 
 

More seriously though, can you still see it in the app? Have you tried allocating an ip address for the speaker? Are you using wifi or Ethernet cable for the speaker? S1 or S2 app?

There are a couple of possibilities, all starting with your controller being unable to reach the speaker for some reason. This can vary from things like wifi interference, firmware version mismatch, power issues, etc.

I’d suggest a network refresh, which may cover a host of these potential issues, unfortunately ther just isn’t enough information in your post to be certain. First, temporarily wire your Sonos speaker to your router with an Ethernet cable. This could require you physically moving it, or a long Ethernet cable, but it is temporary. Then power off your Sonos. Reboot your router. Wait two minutes, then plug back in your Sonos to power. Wait two minutes, watching the LEDs as it powers up and connects to your router, then open the controller and check for updates. If the controller finds any, apply them. Once that is done, you can test. Finally, if applicable, remove the temporary Ethernet cable and or move the Sonos back to where it came from.

Alternately, I would recommend that you submit a system diagnostic within 10 minutes of experiencing this problem, and call Sonos Support to discuss it. Don’t post the resulting diagnostic number here.

There may be information included in the diagnostic that will help Sonos pinpoint the issue and help you find a solution.

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.

Essentially, you just walked in to a car repair shop and said ‘my car doesn’t work, why’. There’s a lot more detail needed if we’re to hone in on what the issue is.