I am not sure if I am missing something or if this may be a limitation with NotePerformer, but even following the instructions here to enable independent voice playback is not allowing a divisi in a string instrument to play pizzicato and arco at the same time.
In my case, the upper division (staff 1) is playing arco while the lower division (staff 2) is playing pizzicato. At the moment both play back as pizzicato.
In general this works fine, so there may be something misconfigured in your specific project. Try reapplying the NotePerformer playback template in the first instance. If that doesn’t work, cut down your project to just the affected player and a few bars and attach it here, and we can take a look.
User error …
I thought there was a single switch to enable independent voice playback for all instruments. Instead, one has to do this for each player.
Curiously, the NP interface did not update to show the different channels (I am quite sure it used to do for other projects). They appeared in Play Mode, though.
Feel free to close this topic / lock / merge it with the other one.
Thank you!