Hi,
Can you load the library in HALion Sonic SE or HALion 6, when these are running as plug-in in Cubase 10.5?
This Dark Planet “software” was available just for a very short time. Later on it was possible to open the library in HALion Sonic (SE) and HALion, so you didn’t need this specific plug-in. The specific plug-in is not maintained anymore. Therefore it’s much better to open the library in HALion Sonic (SE) or HALion. The only one reason to own and use the specific plug-in is, if you open an older project, where you already did use the old plug-in.