Sonar Home Studio: Question about playing audio and midi at the same time

A little over a week ago I had figured out how to do this. I have Windows 10 with Sonar Home Studio, and I would open the MIDI file first, then import an audio file into that and was able to play the audio and the MIDI at the same time in Sonar.
 
I had to be out of town for a week, and when I tried doing this exact same thing this morning, the audio would play but the MIDI would not.
 
I tried opening the MIDI file in Sonar and it played fine, but as soon as I imported the audio file, the MIDI stopped playing.
 
I hope somebody out there knows how to remedy this. I have tried several things.
 
Here is the error message I get:
Can not open registry. {C25C3D7B-0FBC-4dbb-BA9F-3A7DDEE3818D}
 
I click the "close" button on that, and then I get the following error message:
Failed to insert soft synth.
The synth may not be properly installed.


Thank you in advance for your help!
 
 

I'm using the TTS-1 (or whatever that's called — I'm not in front of my computer at the moment).
 
It's the Sonar choice that somebody on this forum suggested to me.

First remove the MS Wavetable from the output, leave your MIDI output set to none. 
This allows Sonar to automatically insert TTS-1 when you OPEN a MIDI file. Always open MIDI files. 
You would choose the MIDI Sport as output if you wish to use an outboard synth for playback.  
 
Check your track outputs both midi and audio and make sure they are going to the correct place.
The midi track output will be the TTS-1 or which ever synth you wish to use. 
the audio track will go to your sound card or a Master buss if you have inserted one.