I'm using Sibelius 4, and I just installed GPO 3, and my notation program can't see the library. I've tried to alter the output device Sibelius uses, but GPO isn't even an option. As far as I know, I've installed everything properly, my drivers are in full working order and compatible with the software, everything else checks out ... I just can't open Sibelius' eyes to the brand new world of good sound.
I have the same issue but dont completely follow what you said.
OK im with you up until loading the sounds onto the sebalius channel. I've downloaded the cables and its showing up, but im lost from then on... could you help?