The first thing to understand is that "Yep Voice Manager" is not a widely known or mainstream software application. Online searches for it often lead to third-party download sites or forum discussions, which is a common sign of either an older, niche tool or an application that's no longer in active development.
For newer keyboard owners, Yamaha built the [64-bit Yamaha Expansion Manager (YEM)](1.2.1, 1.4.2). It is vital to note the compatibility gap: yep voice manager 64 bits download