When entering and selecting notes they play perfectly but when I press P or the space bar the playhead just scrolls through the score with no sound.
I’m using NotePerformer. My audio interface is selected in the Device Setup and NotePerformer is updated and works in other applications.
What if you go to Play mode and choose from the menu Play > Playback Template, and then in that dialog choose the NotePerformer Template?
That helped although it was already selected 
thank you!
When you perform that operation, even if it was already selected, Dorico loads the whole playback template and it often makes things clean.