I am trying to record MIDI tracks to a single stereo audio track. 
Several MIDI tracks are missing in the recorded audio track. 
I am using a MOTIF-XF8 with firewire. This setup has been working .
Is it possible that one of the updates caused this not to work?

Dude, You give zero info on how or what your doing. 
Please describe in steps what you are doing and if this is outboard gear etc??  , inquiring minds need to know! 
 

Let me guess...you have a sequence in the Motif XF with multiple tracks.
 
You want to record the Motif's mixed audio hardware output into SONAR as audio to create an audio track. 
 
The tracks don't appear in the Motif's audio output, so they don't get recorded into SONAR.
 
Yes?

Anderson,
I record all of my MIDI tracks and mix the 16 tracks.
The next step is to record the MIDI tracks to a single stereo audio track.
Then I add effects in the audio track and generate wave files.
 
I have done this many times successfully.
 
Sometime between March 2016 and January 2017 a problem has cause several of the 16 MIDI tracks to be missing from the single stereo audio track.
 
I am using Sonar Cakewalk Platinum with a Firewire interface from my MOTIF XF8 to my computer.
If you have a solution I would be very greatful for any suggestions to resolve this issue.
Thanks,
Tony
 
 

Does your Motif have more than one stereo out? Does it have an internal mixer?

The firewire cable transfers 8 audio channels and the bi-directional midi data. When I record the 16 midi tracks to a single stereo audio track for some reason several of the 16 midi tracks are missing from the audio recorded track.

Its possible that the audio is being routed to different audio outs. If you are recording only one stereo channel the others may also hold audio that is not being recorded. I know nothing about a Motif however if I'm not mistaken it is a workstation. This means its a DAW also.  

John, Thanks for your suggestion. Is there some where in the software that would indicate what audio channel the individual midi tracks are being routed to.
 
The setup that I have been using stopped working after the last update. (I had everything setup to work, recorded a cd just fine, made suggested cakewalk updates and now it doesn't work).

You would normally do all this routing in the Motif, not in Sonar.

SANDERXPANDER, JOHN and all that tried to help.... THANK YOU got it working again.