All sound and playback stopped after I changed the instrument assigned to a soprano part from “Aah to Ooh Choir NoteExp” (the default) to Giant Aah Choir. I have changed it back and to other instruments, saving or not. It doesn’t matter. No project will play now, not even your samples. Please help!
Dorico takes over the sound in the middle of loading the Hub. I used to be able to listen to a Dorico how-to on Youtube and hear my own actions at the midi keyboard, or playback. Now both the system and/or Youtube sound stops as the hub is loading. It does not come back even after closing Dorico. I must reboot.
No project will play using any technique now. Play tab does nothing at all. In write mode, the green bar will show with all the ways to start playback. But it does not move, and nothing plays.
In write mode, my midi keyboard will play the sound of the notes I press, and they are entered, for a few seconds. Then Dorico crashes. Typing keyboard note entry will not play sound, nor will arrowing left or right.
I am using Win 10 on a i7 pc with 16 gig of ram. i have 500gig of disk space free. I’m using a keystation61 keyboard and an Audiobox USB for a sound card.
After a reboot, try running Dorico and before opening any projects, go to Edit > Device Setup, and click the Device Control Panel button to open your audio driver’s control panel: if it’s the General Lower Latency ASIO Device, check that the option at the top of the dialog to force exclusive ownership of the device is switched off.
A little additional advise on Win10: Avoid application-driven sample rate changes. Change sample rates before launching applications at soundcard/interface’s control panel when possible. This is especially true of older Focusrite models. Updating the soundcard’s drivers may reduce samplerate-change driven lockups.
Thank you for your quick replies. We made some progress 
I can play my work again, and midi keyboard entry will sound notes. Dorico no longer crashes in the first few seconds. But it still takes exclusive control of the audio driver. Anything that needs the sound will just hang, including Media Player, YouTube, Pandora and Cakewalk. I have to reboot to get access.
To get to this point, I went into Edit | Device Setup. I found Dorico detected the Audiobox USB ASIO. That does not have an exclusive control option in its control. Just for grins, I changed the driver to the Generic one and turned off the exclusive use there. After a save and reboot, there was no change. I changed the driver back to Audiobox, rebooted, and Dorico started to work. But I need to have everything with access at the same time like it was at first.
Traubitz, there was a driver update. I applied it after my last step above. If I have need to change sample rate I will follow your advice.
(For future reference, I did find an exclusive use checkbox for the Audiobox in the Windows Sound settings. In Playback Devices, a click of the Properties button will bring up another dialog window with the “exclusive use” checkbox. It was checked. I don’t know if that is a change from before. But when I turned it off, Dorico would not play.)