Sonos app says cannot find track

Using WDMyCloud as an NAS with music and pictures stored. The pictures feed to a picture frame but due to some problems with the viewed pictures I did a restore of the MyCloud and thast resolved the picture problem (fingers crossed) BUT now cannot access the music through the Sonos app. from IPhone or Surface. The error message says cannot find that particular track (or any tracks) although I can see them in Windows 10 Explorer. I have moved the music folder about from being into ‘Public’ to being into ‘Shared Music’ but doesn’t make any difference. The pictures folder is sited in ‘Public’ (Not shared pictures) and works fine. Do I have to scan in the IP address page or in Twonky??

Any help appreciated…2019-12-22T00:00:00Z