Hi Ben!
Have you made all the settings for programs and channels in the Playback Devices/Manual Sound Sets tab?
I recommend watching our tutorial video at the following location:
http://vsl.co.at/en/211/1343/1348/243.vsl
and reading the Sibelius 5.2 and Vienna Ensemble Setup guide you can download at the following location:
http://vsl.co.at/en/68/375/377/239.htm
In order to help you better, I need some more information. What VSL products are you using with Sibelius? What is the name of the sound set you are using? Which version of Sibelius do you have (Sibelius 5.2.5 would be best)?
Best wishes,
Andi
Vienna Symphonic Library