Hi,
The problem is a boatload of unused staves (they have no notes and so aren't displayed in the score) which are all set to Piano.
You can use Staff/Setup, and delete all the "Acoustic Grand Piano" staves that are not check marked as "In Part" for the Conductor's Score. These staves have no notes, and are an artifact of how the file was sequenced.
This is a not-uncommon problem with some sequencers (the software and the folks who use them
).
After doing that, all plays as it should - at least it did for me
ttfn,
Sherry