I find Dorico to be quite finicky about playback on my Windows 10 systems. I almost always have no sound after starting, but if I go to the Play tab and select (even the same) playback system on the righthand side (under VST instruments) it usually comes on. Doesn’t seem to matter whether it’s NotePerformer, Pianoteq, or Symphonic Orchestra, they all seem to behave similarly.
Addendum: I was just in a state with NotePerformer where it would play back when I clicked on a note in Write mode, but when I hit play I got nothing. Seemed to get fixed when it when to the Playback Templates menu and clicked on NotePerformer (even though it was selected). The VST helper window went away and didn’t come back, but I got playback, so I counted that as a victory.