Sonos has just removed the ‘play from Android phones’ much as they did from iOS phones several years ago due to changes in the OS. Your best bet would be to read this thread:

although there are already several other threads that cover the same ground. 

Hey thank you Bruce, I will take a look.  Best wishes

iPhone?  Stream via Airplay.

https://support.sonos.com/en-us/article/stream-airplay-audio-to-sonos

I was certainly taking the assumption, due to the timing, that it was an Android phone, but if not, @jgatie  is 100% right, and something I’ve done since Apple closed iOS to the ‘play from this device’ method that Sonos had been using. 
 

I can well imagine Sonos is not happy about this change to Android, either…but to me, it’s not an unexpected change. In fact, I’m amazed it took Google so long to come to the realization that it was a potential security issue, much as Apple did. Not Sonos’ fault, just unfortunate that so many folks used this ‘loophole’ method. 

In what way is it considered a security risk to stream from your phone ? 

Instead of the phone streaming to the Sonos device, Sonos devices stream directly from the source, so in order to stream the files on your phone, the Sonos devices exploited an open external access path which has been tightened up in iOS.  Not sure what Android has done, but the same type of external access was used there also.

Thanks for clearing that up. So the only way for it to work again was if we would get Chromecast support.. wich is probably never going to happen... :-( 

Again, a feature that should be provided by Google.

I find the situation most interesting, given the loss of millions by Google to Sonos on Friday for patent infringement. If I were a tin foil hat type person, I’d suggest there’s some bad feelings on Google’s side and a consequent desire to make things as difficult as possible for Sonos. Which means punishing us users. 

You say you ripped the CDs so that must have been on a PC or Mac. Just leave the files on there and set up a Sonos local library on that device.

Thank you for all your replies... I followed Airgetlam's link to successfully connect my NAS to the soundbar!

Best wishes, Tim