I am having the same problem with my Hi-Q SampleTank sounds.
I just did a re-install of biab v 15 and then installed updates 415 and 417. I let the installer use the default paths during the installation. Real Tracks, Real Drums, and everything else seems to be working fine.

I can also see that the C:\bb\DX Settings folder has references to the Hi-Q sound sets. The only Hi-Q sounds I can find after the installation are a set of woodwinds and synth sounds in the following folder:
C:\Program Files (x86)\IK Multimedia\SampleTank 2.5\Instruments\Band-in-a-Box.

I searched my whole drive and there are no other SampleTank sound sets present on the computer. Am I missing something in the install procedure? My original purchase was for the 2015 biab megapack.

Your help is greatly appreciated.
Thanks!