Whenever I see this message, closing down the app and reopening brings up my system every time.

(I’m not saying this is ok, just providing a work around)

I'll give it a try but kinda seems like a hassle to get my music.

Hope they fix it

I get this exact same experience. Updated Sonos app for Android is really poor. Takes an age to start up, never recognises my speakers when I first open the app. As melvimbe suggests, I have to shut down and restart once or twice to get it to do what it's meant to.

Come on Sonos, you can do better than this

@martin_m 

As you are on Android, the best thing for you would be to delete the updated app, and download and install the APK of the old app version 16.1. (Google ‘Sonos app 16.1 apk’ - APKMirror is a decent site, as far as they go). 

And then turn off auto updates for the app until the issues are fixed.

Same here. It's horrible. 

Same. Awful experience. Slow loading up and detecting the system or most of the time says system not found. 

I'm getting the old app. Everyone says it works great again if you jsut download the apk

Try updating the app with today’s just-released update in case it helps...

The Android app hasn't seen my system in a few days now. But the Tidal app can, which is usually the one I have trouble with. But you can't control the volume from it. 

But! Changing the volume on the speakers themselves take a few seconds to respond, so I keep going too far, making it too quiet or too loud, and my wife is sleeping! (She works midnights!) 

I'm done. I also have a Port for my CD player, but that kept cutting out yesterday, so I can't even listen to CDs now. 

Sonos has become a joke. I can't even sell my stocks now unless I want a hefty capital gains loss. 

I’m sorry you are having difficulties, but the app and system are working fine for me, so it is possible.  (I say “fine”, but obviouslyly there are frustrating gaps in functioality.  I do also get the “System Not Found” message sometimes, but I have found that turning my phone’s WiFi off and on cures it every time and is marginally quicker than closing and re-opening the Sonos app.  But fundamentally, my system and app still work without delay, and I still enjoy my music.

So I think there is a good chance that you are blaming the app and not considering the possibility that something else is wrong, which might be fixed with some attention.  Up to you, of course…..