I have Hallion 5 and Halion sonic 2 (full versions - had these before 7.5 was released) and have a similar problem
The only instrument sets showing in Halion are the 4 basic ones. No Model C, for instance. And not the orchestra, which I bought some time ago.
Also, other intruments like Tribewerk and Hypnotic dance are no longer showing within Halion.
I think the patches themselves might be there, but not the groupings.