Hi Cantankerous,
Actually, the first post in this thread just tells us to contact Steinberg support so that they can tell us what to do. I did that, but have had no reply.
I did not upgrade to H4 because it took so long to arrive that I went for Kontakt instead. My main interest in H5 at the moment is Haliotron and Model-C (which I hope will be good enough to replace the last 32-bit plugin I use - NI’s B4-II, although I doubt it).