Oh and to get Halion to see the library double-click on any of the sound files which will open the Halion Library Manager (might have name wrong) and register all the sounds in that folder. The download manager by default puts Iconica in 4 different folders so you’ll need to do this 4 times - once for each folder. But the Library Manager will help you move them all into a single folder if you prefer (or you can move them all into a single folder before registering any of them & only do it once).
Also the download manager will only download one huge file at a time. So maybe the sections you couldn’t download were just waiting for a different download to end. Smaller files can load in parallel.
The instructions from Steinberg for all of this was kinda lacking.