I believe this issue may have started with the latest 126.96.36.199933 update (but not certain).
1) Drag Presence to a track
2) Select Rock Grand (or anything)
3) Arm track by pressing "Monitor" and record something (I can hear the Rock Grand fine) and midi is captured just fine.
4) Press Start to playback what was just recorded (I can hear nothing)
5) During this Start/playback the Activity Meter raises for each pre-recorded midi note, also the Presence keypad also shows keys being pressed (from pre-recorded midi), but again no sound.
*) During the above if the "Monitor" button is pressed in, I can press a key on my keyboard and hear it but still the record notes make no sound.