I can't figure out why sometimes I get sound and others not.
I start the Drum machine (DR880) plugged in to USB
I start Sonar and add a new TTS-1 and it makes an instrument track with input echo on.
I set up Preferences to MIDI Devices and add the DR880
In Project> MIDI I have checked everything (in desperation-is there something that should NOT be checked?) 
I apply it but no sound. 
The track is enabled.
Input set to DR880 MIDI Omni
OUt to master

I must be missing some step.

Yes the step is:
Make sure the USB connection is fitting snug in the computer. Moving the unit around can apparently loosen it up.

Duh.

Moving the unit around can apparently loosen it up.

Be careful with that, man. I thought I had wrecked the USB out on my padKontrol moving it around carelessly with the cable still attached. It stopped working completely and the cable was kind of flopping around in the port. I freaked. Eventually I tried swapping out the cable and fortunately it started working again but the port is still kind of loose so I have to be ultra careful with it.

Friggen' Korg, man. I can't believe they made the port so crappy on something designed to be bashed away at by wannabe percussionists. It was really cheap though and it does a good job so whatevs. Cheers.

Same issue for sure. Had me so baffled and ,because I'm a midi noob, I was sure it had to be some setting I had screwed up or missed.
I'm going to attach some velcro to the computer and the cable and secure the cable. 

You figure with all the engineering that goes into these things they make sure the most crucial connector was solid. lol

Glad you got it sorted out.

@M_Glenn_M

Coming from similar background with a DR880.. I tried to add the DR into my setup..

Initially, I did all my drums programming using the DR (being comfortable with that work flow, but not necessary easier - but I don't know yet), and sync it with X1 for other tracks. I would then record the DR audio to X1 last, while in sync.

Next, I experiment with recording DR midi instead of audio (still did the drums programming on DR), and I would just use the DR as sound module. I did it this way, so I can save the drums midi together with X1, and not having to manage saving DR memory separately. But this introduce a new problem - editing drums becomes much more difficult. I mean, in DR, a single pattern that is used over and over again in song mode - you only need to edit once, but once expanded into a song in the X1 midi track, the same pattern is now scattered all over.

When I learn to use the Session Drummer 3 / step sequencer - I see the light. All the problems solved. Programming drums become much faster using the step sequencer. I do not need to use the DR at all.

About the only thing I missed is you cannot loop record/edit over a pattern real time.

Reading about your setup, you record the DR as midi to Sonar, then use the midi to for TTS sound module. Why not just sync the DR and record it's audio? You may want to do this for existing songs already done on the DR, but for new drums, learning to use the step sequencer with SD3 or SI Drums will further simplify your task.

Thanks for those tips. That is likely the way I am headed too. I
 am already familiar with SI Bass and strings so will try SI Drums. I have also heard good things about SD3 and will try that too.
So much learning to do! It's a wonder I get anything actually done.