Cannot get output (sound) from plugin other than Bus[0]

Windows 10x64.
JUCE 5.4.5

I cannot for the life of me figure this out.
I have a DAW type application (this is not a plug in) that is loading a single
plug in currently Steven Slate Drums 4 (SSD4). SSD5 will not run when a debugger is present.

SSD4 has a built in mixer so one can assign each voice to a bus.
‘Stereo 1’ (BusIndex[0]) always works, meaning sound happens.

If I assign an instrument to any other bus then no sound is produced for that instrument.

This is what the important information (at least what I think is important)
from the plug in one I have loaded it:

AudioProcessor::BusCount(Output): 16
AudioProcessor::TotalNumberOfOutputChannels: 24
// BusLayout=(PlugInPtr->getBusesLayout)(); This Is The Active Bus Layout?
BusLayout::NumberOfMainOutputChannels: 2
BusLayout::NumberOfMainInputChannels: 0
BusIndex[0]: Name=1 NumberOfChannels:2
	IsEnabled: Yes IsEnabledByDefault: Yes
	AudioChannelSet::Description: Stereo
BusIndex[1]: Name=3 NumberOfChannels:2
	IsEnabled: Yes IsEnabledByDefault: Yes
	AudioChannelSet::Description: Stereo
BusIndex[2]: Name=5 NumberOfChannels:2
	IsEnabled: Yes IsEnabledByDefault: Yes
	AudioChannelSet::Description: Stereo
// Ommited 3-14, but they are there, all enabled
BusIndex[15]: Name=24 NumberOfChannels:1
	IsEnabled: Yes IsEnabledByDefault: Yes
	AudioChannelSet::Description: Mono

AudioProcessor::BusCount(Input): 0

int juce::VSTPluginInstance::prepareToPlay()

numOutputBuses:16
maxChannels:24

In my audioDeviceIOCallback() I am doing this:

{
 // I am using a ASIO AudioDevice.
 // There are no inputs enabled so numInputChannels:0
 // THere is one output pair enabled so numOutputChannels:2
 ................... Some Code

  if(this->Processor!=nullptr)
  {const ScopedLock sl2(this->Processor->getCallbackLock());

   if(!(this->Processor->isSuspended)())
   {
    if((this->Processor->isUsingDoublePrecision)())
    {
     (this->ConversionBuffer.makeCopyOf)(Buffer,true);
     (this->Processor->processBlock)(this->ConversionBuffer,this->IncomingMidi);
     Buffer.makeCopyOf(this->ConversionBuffer,true);
     // Am I Leaving A Lot Of Memory Behind Here By Not 'Emptying' My Converion Buffer?
     // On The Other Hand I Only Have One Processor Which Will Probaby Use The Same Amount
     // Of Data Each Time?
     // See audioDeviceStopped()
     }
    else // Not Using Double Precision
    {
     // (this->Processor->processBlock)()
     // -> juce_VSTPluginInstance::processBlock()
     //   ->juce_VSTPluginInstance::processAudio()
     (this->Processor->processBlock)(Buffer,this->IncomingMidi);
     }

    return;
    } // End if(!(this->Processor->isSuspended)())
   } // End if(this->Processor!=nullptr)
  } // End Scope Block For Lock

........................... Some Code
 }

When juce_VSTPluginInstance::processAudio() is called:

buffer::numChannels:2
tmpbuffer::numChannels:24
vstEffect->numOutputs:24

So, in the end this all looks like it should be working, but anything
occurring on any channel other than 0,1 (Stereo 1, BusIndex[0]) is not coming through
(No sound produced).

What am I doing wrong?

Thanks in advance for any pointers.