Halion Suddenly Stops Working

I am working on a MacBook Pro 2021 M1 Max, running Dorico in Rosetta mode. I load the Halion playback template from the menu, hit Apply and Close, and nothing happens. What’s weird is that I have been doing this before in other projects and it works but always stops working randomly. What’s the deal?

It’s hard to say from the information provided. Could you create a new project, add a player, and input a few notes: does this project play back? If you open the Mixer window and play back, are the faders all at sensible positions (i.e. not all dragged right to the bottom)? Do you see any metering?

If you go to Play mode in Dorico and select the track corresponding to the instrument in your score, then click the little e button in the Routing section of the Track Inspector to show the HALion window, does it appear? Do you see any metering in the HALion window during playback?

If none of this helps, please choose Help > Create Diagnostic Report and attach the resulting zip file here, and we’ll take a look at the logs.