Thank you both for the responses. I've contacted the shop, so we'll see what they say.
I personally have not used the expansion manager so add any packs. When I look in the expansion section it has the four or so region ones that I believe come standard with the SX900.
I guess regardless of how they got there, what's with the missing voices? Are the styles looking for a voice that isn't there? In principle should voices have been added alongside the styles, so when the style went looking for the voice, it would find it? Put another way, the style doesn't know to look for a similar voice that is standard with the keyboard, and when it can't find what it wants, it shows as nothing?
Since this is my first arranger, I'm learning about adding things from prior keyboards, and how not everything plays nicely!
Thanks again.