OK, I've been troubleshooting. I have the 2016 UltraPlus Pak installed, along with the 430 update. I've re-installed at least three times from the portable hard drive, and still cannot get my RealTracks to install correctly. Finally, I dug down and got the following two messages:

There are 853 sets of xt2/st2 files missing from your BB folder C:\bb\. You should look elsewhere for these missing files. e.g. c\bb\RPedSt03.ST2 and C:\RPedSt03.xt2
1424 RealTracks have folders in C:\RealTracks\, but no r*.st2,r*.xt2 files in the BB folder. Either find missing r*.st2 and r*.xt2 files and copy them to the BB folder or re-install RealTracks. Then press REBUILD button to re-build the list.

I'm computer savvy, so please point me in the right direction. BTW, of course I've used all the BIAB default file locations - I'm a long time user, and NEVER change the default locations!