It turns out there are two different installers - one for Full and another for Update. The Full installer is 11 GB, where the Update installer is only 2 GB. I was using the Update installer, despite having uninstalled my existing Cubase 8.5. The Update installer - quite reasonably - only installs stuff that has changed, where the Full installer, of course, does it all.
Cubase 9 missing plugins!
I did a complete uninstall of my Cubase 8.5, cleaned up all manner of 32-bit stuff on my system, and did a fresh install of Cubase 9 Pro. Halion Sonic SE & Padshop are nowhere to be found. I’ve uninstalled and reinstalled Cubase 9 again, no joy.
I see one other person has posted with this same problem. Does anyone have a suggestion? I’ve written to support, but I don’t expect a rapid response from them on a weekend.