I should also add that I can still trigger a drum with the mouse but not with a midi keyboard.
 

that is step 2 in the process I provided above.
Might want to provide what version of SONAR you are using.
 
BTW, I removed the "Answered" flag from this thread as the problem has not been addressed.

I'm running Sonar Platinum 23.10.0.14. The keyboard test failed.
 

The virtual keyboard failed to trigger SI Drums,
yet SI Drums plays from the plug-in UI
and input echo is enabled on the instrument or MIDI track.
 
correct?

I have mistaken the virtual keyboard for the "give all keystrokes to the plug in on the synth' I will follow your guide and try again later tonight when I return from an appointment. Thank you for staying with me.

I'm not completely following, but I had a problem with my MIDI keyboard not sending anything to SPLAT after a major Windows update - whichever one was right before Gibson blew up Cakewalk.  I was able to get it working again by deleting the TTSSEQ.INI and AUD.INI files and letting SPLAT recreate them.  I still have to do that occasionally, even with Bandlab Cakewalk.

Success today!!!!!! After following Scook's  advice I have full function with both of my midi controllers and the Cakewalk virtual keyboard. I had to run a search to find TTSSEQ.ini  buried in "USERS". I should have removed this earlier, it would have saved me hours of frustration.
 
I will work with the midi devices for a few days and report back if there are any lingering issues. Thanks to everyone who contributed to my questions.

Did you save a copy of the original TTSSEQ.INI? Would be interesting to know how it differed from the new one that  Cakewalk will have created to replace it.

Sorry I didn't, you are right, it would be educational.

Glad you got it sorted in any case.