Piano II plays back, Piano I does not

I’ve just finished copying a score for two pianos and SATB choir. The choir parts are fragmentary, for cues only — the only layout that will be printed is Piano I & II. I noticed while working that Piano I wasn’t playing back, and just now I noticed that the choir parts are not playing back either (not that they matter in this case). Piano II plays back normally.

I don’t normally bother about playback, but I notice when it’s missing! I haven’t knowingly changed anything in Play mode and wouldn’t know how to if I wanted to, but I can’t swear I haven’t clicked something accidentally and broken it.

I’m really a babe in the woods when it comes to sound, and I’m grateful for any advice.

I’ve attached the beginning of the first flow in case it helps. Change .zip to .dorico to open.
Requiem fragment.zip (627 KB)

Everything works normally here (Mac OS 10.11, using the default Halion playback) I’m assuming you’ve tried restarting Dorico and/or your computer. If that doesn’t work, maybe provide some details about your computer and playback system?

Thanks for the response. Both Dorico and the computer were restarted many times while I was working on this job, so that’s not the solution.
Computer is a Dell XPS 8920, 64-bit, running Windows 10 Pro, 1803 update installed, Intel Core i7-7700 3.6GHz, 4 cores, 16.0 GB RAM. Further details on request.
Playback system: I don’t know what to tell you, but if you tell me where to look I’ll report what I find.

Hmmm… everything appears normal here as well…(W7)… If you go Edit/Device setup… what are your settings?

One of my very favourite works!

It also plays back just fine for me. I suggest you try doing Play > Playback Template and reapplying the default playback template to see if that sorts it out.

One of mine too. The arrangement for two pianos dates from 30-odd years ago and has a bit of a history.

I went to Play > Playback Template and found three options, HSSE (elements), HSSE+HSE (Pro), and Silence. HSSE+HSE (Pro) was highlighted, I clicked on it again and OK’d out of the dialogue. Back in the score, nothing played back — not even Piano II.

Went into ‘Halion Sonic SE’, understood nothing of what I saw, but somehow managed to close it. Closed the score and Dorico.

Reopened score, no sign of Halion Sonic SE at first. Clicked on Play > HSSE (Elements). Halion Sonic SE sprang into life and it looked like it loaded each of the instruments I am using. In the score I had sound from both Pianos. Hooray! Also the choir. Back in Play mode, clicked on Play > HSSE+HSE (Pro) — Pro is better than Elements, isn’t it? Score still had sound.

I’ve very little understanding of what happened there, or how I lost sound in the first place, but it’s working now where before it wasn’t.

So thank you Daniel, and also Vilnai and Fratveno for responding.