My apologies if this belongs in another subforum. I have been having issues getting HALion to work on my Macbook Pro running 10.14, with no external drives attached.
Firstly - I downloaded the sounds installer via the Steinberg Download Assistant (which then proceeded to download the file via Chrome. Intentional?).
I then ran the dmg file, which seemed to run and install without issue. However, running the Steinberg Library Manager revealed that nothing was installed. I looked in both /Library/Application Support/Steinberg/ and ~/Library/Application Support/Steinberg/ for any HALion files but was not able to find any. I then copied all of the files from the Additional Content folder in the dmg to the VST Sound folders in /Library/Application Support/Steinberg. This caused the files to show up in the Library Manager.
However, when running Dorico, no HALion playback works. Loading and playing other VST instruments works without issue. Opening the edit panel for HALion in the Play window reveals the HALion GUI, but there are no instruments as options. I have attempted to attach a screenshot below. Hopefully it works.
Did you definitely install the “big” Dorico Pro 3.5 Sounds Installer (8.6GB) as well as the Dorico application installer? You can find that installer in Steinberg Download Assistant, or here.
I did download the Sounds Installer. However, since it doesn’t seem to actually install any files when I run it, I manually copied the files, and I don’t know if I put them in the correct places. HALion (all 87 files) is currently located in /Library/Application Support/Steinberg/Content/HALion/VST Sound/, and the Indian Drum Basics and Olympus Micro Choir are in /Library/Application Support/Steinberg/Content/VST Sound.
What version of Dorico do you run and exactly which preferences did you delete?
If you are on Dorico 3.x you need to delete the folder /Users//Library/Preferences/VSTAudioEngine3 as well, as that one contains the database file for the scanned contents. A deletion of that database file will enforce a rescan on the next startup.
When you double-click one of the .vstsound files, it should launch Steinberg Library Manager and install the sounds. Certainly if Steinberg Library Manager is showing no installed libraries, HALion Sonic SE won’t be able to find any sounds.