Halion 3.5.0.593 can't open/load sound sets

Virtual instruments HALion
1

I know this is a bit old, but I’m trying it out before upgrading. I’ve installed Halion 3.5.0.593 on my Windows 10 PC. It installs fine. I’ve placed all 5 HSB sound sets in a folder. I’m using Samplitude Pro X3 as the music software. Halion is there in the VST list. It opens fine. The MIDI is set up fine. When I play a keyboard note, I see it register in the monitoring of the track. So, I click Browser button, locate Halion and navigate to the HSB files, select them and click Open. Nothing happens. Interestingly, there is a red exclamation mark beside them (see attached images).

IMG_5007
IMG_50073024×4032 3.5 MB
IMG_5008
IMG_50083024×4032 3.41 MB

I’ve tried various Windows Compatibility modes, Run as Administrator, etc. Still, no sound set will load up.

Any ideas, or is the version of Halion just too old?

Thanks in advance!

Seamus