are you talking about a situation where the presets show and they apparently load with now error messages? or is it a situation where it says library not found?
I had a problem with The Grand 3 where everything looked ok, everything was installed in the default locations. I did notice when loading a preset it took like 0.001 seconds to load and I got no sound (Windows 11).
The plugin seemed to work like normal. Steinberg support nor I did make sense of it. I had to clean out EVERYTHING. Uninstalling , but also delete all about The Grand 3 in the programdata folder and the roaming folder on my PC. Then I did the reinstall and it worked again like expected. I did a few reinstalls before that, but it seemed I didn’t clean out everything and I had the same problems.
So your problem sound familar to me, I guess just one of those things that makes no sense.. then a fresh start and back to working again without making any sense. I had Halion and all other vsti work just fine
but if there is no presets in Halion have you tried Retrologue or other Steinberg products? are they missing presets too? then maybe there is something wrong with how they point to the presets. The other products you use mostly use their own internal presets systems inside their instruments?
So if you open Halion and choose single instrument check out the right side where it says “mediabay” or “browser” and pick from “browser” pick “VST Sound” and there should be “Halion Content” below there. Pick something there and see if you atleast get something going
One thing that worked for me is to open the media bay, and deselect the main drive or the areas/insturments that you have trouble with (can be tricky to figure out where things are) , close off the media bay, quit Cubase. Open Cubasae and then reselect the things that you deselected before.