I am not sure why the Expansion Pack did not install correctly.
Most DimPro and Rapture expansion packs have two parts: mulitsamples and programs.
For 64bit installations the default multisample location for Rapture is located in "C:\Program Files\Cakewalk\Rapture\Multisamples". The programs are always located in "C:\ProgramData\Cakewalk\Rapture\Programs". Note ProgramData is a hidden folder.
To perform a manual installation, copy the multisample folders into where ever the other multisamples folders are located and copy the program folders into "C:\ProgramData\Cakewalk\Rapture\Programs". Once everything is copied to the proper locations, refresh the program list by launching Rapture, then opening the Rapture Program Browser and pressing the F5 key.