Maybe check if the Sonos App has been granted storage ‘permissions’ within the android device settings.

As I recall, the Sonos app used to only know about the ‘standard’ location in device memory for Android devices, and wasn’t able to ‘see’ other music locations on the OS, but it is possible that this has changed, as I’ve not really paid attention for several years, and use iOS devices. 

Ken,
I checked storage permissions, and they are granted to sonos app.

Bruce,
I am ok, if it is working as you described. But than is strange why I can see files on SD storage which were there before installation of Sonos app.

Two different apps looking for that storage location. The Sonos app, to my knowledge, has never been able to access the non-standard music file location on Android, only the ‘default’. Likely any music app designed to play directly, instead of the way Sonos plays, can see it. You have to remember, the Sonos app isn’t really ‘playing’ the music directly, it is sending a signal to the software on the speaker, and telling that software ‘play the music that you can reach in this location’. 
 

Playing music directly from a mobile device, be it an Android or iOS device has always been a problematic addition to the Sonos system. Sonos is ultimately designed to work with ‘always existing’ music, be that on a PC/Mac, an NAS, or a stream from the internet. Playing music from a device which can ‘disappear’ from the network at any moment as you leave home makes it hard for anyone else to access that music from your system. It’s one of the reasons Sonos doesn’t allow that type of music to be stored in a Sonos playlist. If the mobile device isn’t in reach of the network, there is literally no way for someone using the Sonos to ‘play’ that music. 

Hi @jadro 

Welcome to the Sonos Community!

The Sonos app simply forwards the contents of the Android music library to Sonos. If there are tracks missing, they are likely missing from the Android library too. The simplest way to resolve this usually just to reboot the phone, though apps can be found that will rescan the phone’s storage for media. Note that it will take some time after the reboot for indexing to be done in the background by Android.

I hope this helps.