I've had Sonar Platinum for a while.  Tried Drum Replacer on an older machine, it's there, but disabled.
Installed to a newer 64-bit power house, it's there, but disabled.
I installed and re-installed Drum Replacer via CCC.
I've found the Excluded PlugIn and tried it Enabled, too.  Put it back Excluded as mentioned in these forums.
But no matter what I do, I can't get any of the Drum Replacer submenu items to become enabled.
 
I've tried selecting an entire track audio clip.  A small portion of a track's audio clip.  It doesn't seem to matter.
I can't seem to get "Create Region FX"  or  "Open Editor" or any of them to come up selectable in the menu.
 
Any ideas on the steps I'm missing?
 
Regards,
 
Carl
Platinum Version 22.7.0 Build 41 [2016.07] - x64
Windows 10 Home, Intel i7-6820HK @ 2.70GHz x2, 16.0GB, 64-bit OS, x64 processors
 

I've run into this problem myself and never could figure out why. Sometimes it will work and sometimes not. I only responded so your post wouldn't fall off the page.