I think there's a problem with Rapture Pro with the following.  Sustain (CC64) will only work if it's being sent from a midi keyboard (with sustain footswitch) that is transmitting on Channel 1.  It will not work if keyboard is transmitting on higher channels 2 thru 16.  Can someone else please test this?
 
I've tried this with 2 separate keyboards running on completely separate Midi Interfaces and both fail this test - see config below
Same problem if standalone or VST within Cakewalk.  I do not have this problem with any other synth like Zeta, SI Instruments, etc, etc.  Meanwhile, I have a ticket into Cakewalk support and awaiting an answer.
 
It says in Rapture pro pdf manual that the following controllers are hard-wired so there's no configuring a workaround in the Mod Matrix and would be a pain anyway if you had to alter every patch:
• CC7 = Volume
• CC11 = Expression
• CC64 = Sustain (can be enabled/disabled per-Element using display control)
• CC66 = Sostenuto (can be enabled/disabled per-Element using display control)
• CC73 = Global Amplitude Attack
• CC72 = Global Amplitude Release
 
Config:
DX7 with Grey Matter running as midi controller --> Steinberg UR22 Midi I/F --> Cakewalk (or Rapture standalone)
Kaysound MK-4902 --> USB Uno Midi I/F --> Cakewalk (or Rapture standalone)
 

Solved - my answer was in this previous post:

 
The fix was to select a channel under the C dropdown for that track.  Struck me as odd that doesn't seem necessary for other VST synths - at least none I've discovered so far.  Anyway, guess I'll cancel the ticket with support.

I guess my previous post link didn't get pasted in.  Not sure how to do that.  Anyway, if you search for this in this forum, you'll see previous post:

[Solved]Rapture Pro and Sustain pedal problem