Is this a limitation of cakewalk instruments?  I can't get any of the basses in Dimension Pro x64, SI Bass Guitar, or Cakewalk Sound Center to play a note below third string oopen (A2).  In addition, I can not get any note on the 4th string below the 7th fret (B2).
Lo/Hi Key is set to 1/127 in Dimension Pro x64.
 
Thanks for any input

Not a limitation of the instruments but how the sfz files are defined. To extend the range of the instruments create new sfz files or modify the existing ones to suit.

Thanks for the input.  However, when I try and edit the existing sfz everything is fine till I try to save it to the same folder.  Then I get a " not authorized" type message.  I am the admin on this computer and am set for full permissions etc.  What is next??

The sfz files are plain text files and Cakewalk applications exercise no control over the files  so it is a windows configuration issue possibly a read only flag on the file or directory.