I am using the 60 day trial to decide whether to upgrade from X3 Producer and have downloaded the new Platinum update. It seems to have a bug in the new version which wasn't there in the old one (or X3 Producer).
Drag a MIDI file into Sonar with nothing else loaded. Add Cakewalk TTS-1 (MIDI Source, First Synth Audio Output).
Select all the MIDI tracks and then click on the Tracks drop down and "Selected Track Outputs...". Under MIDI outputs it should show Cakewalk TTS-1 and my MIDI interface but the list is empty. Also note that Cakewalk TTS-1 is available on each channel's individual output selector.
Also the new version is now finding 209 plugins (was 258 and still is 258 in X3 Producer).