No sound with movies on Nvidea Shield. Series all work fine.

Am running Nvidea Shield as a server, all files on a synology nas, with a full blown home theatre system. As of yesterday NON of the files in my movies library are producing any audio at all. Tv shows library no problem!! Am running PCM on the amp, passthrough on the nvidea all of which worked fine till last night. Am stuck! It seems to be something in the nvidea settings, as movies have sound on tvs, pcs, phones etc. As only movies don’t have sound I don’t know what to do. Tried changing settings on the nvidea but there isn’t that much to change, and as I’m getting audio from the TV shows library it’s even more confusing.
Any ideas PLEASE?