This issue came up after a VS to Artist upgrade. TTS has the EDIT function at top of Synth. When you push the button it brings up a panel that allows you to change parameters for specific instruments. For Pianos and Bass the panel provides a section (in the middle) that controls Filter, Character, and Tone controls. After the upgrade , when you turn on this section, silence is heard even thought the MIDI lights are flashing. Turn the section off and sound comes back. This occurs in all of my projects (except 1) that converted AND anything new I create. Any idea what is going on?.

This issue goes back many years. You'll just need to use equivalent track FX with separate audio outs for each instrument (4 stereo or 8 mono with hard L-R panning per instance of TTS-1).

I believe the plug-in goes silent only if the MID tone control is set to zero when toggling the On/Off button. As mentioned above, it has been this way at least since X1.

The TTS-1 effects are convenient but not really worth bothering with. As said , best to use multiple tracks output and use audio plug ins or pro channel to tweak things. I still use the Reverb and the Chorus on  simple stuff like an Organ. But forget editing beyond that.
TTS-1 has only 4 channel output so if you wish more instruments than 4 you need to add more instances of TTS-1.
In the end it's better to look at the higher quality VST's like Dim Pro and Rapture.
 I love good old TTS_1 and it has served me well for a long time on many, many tracks but I certainly have found    better sounds in the huge collection we have on hand. It's time consuming digging around but time well spent.

And the TTS-1 synth is the only multi-timbral GM synth included with Sonar.  That matters if you wish to bring a multi-track (Type 1) MIDI file into Sonar, and hear a close approximation of the original arrangement.

Thanks Folks. Yep the MID tone control at ZERO is the problem. turn it ether way and it works more like a volume control. Interesting that this bug has been around so long and can't  be fixed by Cakewalk.

Cakewalk may not be able to address the issue, there is a lot of Roland in this plug-in.