Not sure you’ve really asked a question, but if you have, I’d suspect some sort of wifi interference involved in making this speaker ‘unavailable’. Note that interference can come from outside your network, no radio signal lives by itself. 
 

At the very least, I’d recommend a reset of your network by unplugging the Sonos from power, then rebooting your router. Once the router comes back up, plug the Sonos back in. It may not fix your issue, depending on what you’re experiencing, but it certainly won’t hurt, and there’s a chance it will indeed help. 

Sorry… Why is my Roam SL losing connection and showing offline in the Sonos app.

I have rebooted my wifi, unplugged and shut down my Roam SL several times and it still won’t stay connected. I have the Roam SL sitting on the charge base all the time. I have 3 other Sonos speakers that don’t have this issue but they are not the Roam SL. 

Likely for the reason listed in the FAQ I linked. 

Unfortunately, I’m not a Sonos employee, so if you were to submit a system diagnostic within 10 minutes of experiencing this problem, and call Sonos Support to discuss it, I still wouldn’t have access to that data, so my responses are based on previous experience, and not hard data that I’m reviewing. 

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 phone folks, they have tools at their disposal that will allow them to give you advice specific to your Sonos system and network.

Hi @BAnsOnLn 

Welcome to the Sonos Community!

You haven’t added which Sonos products you own to your personal profile, so the community is unable to see that you own a Boost.

The Boost creates a wireless network for all non-portable Sonos devices to connect to. As the Roam SL is the only product you have which is portable, it is alone in connecting to your router’s WiFi and it is no coincidence that it is also the only device having problems. You will likely need to adjust some settings on your Orbi router, or move some devices away from it.

As @Airgetlam suggested, I recommend you get in touch with our technical support team, who have tools at their disposal that will allow them to give you advice specific to your Sonos system and what it reports, and your network.