Strange sound behaviour when copying

I have transcribed a full score for a smaller group. Having installed the full score as a project I created the chamber group as an extra set of instruments and did the transcription in situ. On completion I was able to select the chamber group instruments and play the selection without a problem.
I then created the chamber group as a separate project and copied and pasted the chamber music notes from the original project to the new project.
Although I am able to select and play individual notes using the mouse with the new project, when I try to play the piece as a whole I get no sound using the transport or when I select an individual instrument or group of instruments and press P.
This is using the latest version of Dorico and NotePerfomer.
As far as I can tell all my NotePerformer settings are correct but I did notice that the NotePerformer original display tells you to ‘play back from the begining’ to load the sounds but as this has no effect I must assume that the sounds are not being loaded.
Any help would be appreciated.

Did you go to Play and (re)Apply the NP Playback Template? That’s what I would try first.
Also check to make sure the Metronome/Click track in the Mixer has not been solo’d by accident. (It sometimes happens.)

Yes, I think going to the Play menu and choosing Deactivate All Mute States and Deactivate All Solo States would be a good start.

I’d also try under Edit > Device Setup setting the sample rate to a different value, wait 3 seconds and switching back to the old value. After that, does playback work?

Thanks for all the suggestions. Before they appeared, I actually got round the problem by exporting the chamber project as a musicxml file and reading it back in. There are always one or two items to re-input (text and cesura’s) but the sound was restored.