Just loaded the latest sonar update.  TTS-1 (yeah, don't laugh, I like it) won't respond to my keyboard.
1)  Inputs are appropriately setup in preferences.
2)  Other softsynths have no problem.
3)  Input is set to my keyboard, just as the other softsynths.
Anything obvious I'm missing?

Hi. If you open TTS, are you able to play with the notes (in TTS) assigned to each channel? Have you somehow changed default MIDI output to GM?
Best of luck.

The IM button?

Channels, banks and patches set in the MIDI track pane?