Why is there no audio thru from mic -> usb in this simple sketch? (whitenoise works)

[Mike5000]

Can someone spot why there is no audio from the mic to the USB out? (Whitenoise works well to the usb2 device).

Teensy 3.6, Audio board.

I know the mic works because other sketches let Audio thru from mic with no problem.
I use VisualTeensy_V0.84 to compile the project. TyTools is used to transfer the target.
This works fine on other projects ....

I did try to compile the same sketch in the standard Arduino IDE. The same problem occurs there, so I doubt its the compiler / toolchain. There must be something I do wrong in the sketch ...

#include "Arduino.h"

#include <Audio.h>
#include <Wire.h>
#include <SPI.h>
#include <SD.h>  
#include <SerialFlash.h>


AudioControlSGTL5000     sgtl5000_1;     
AudioInputI2S            i2s0;                            // INPUT from sgt15000_1 
AudioOutputI2S           i2s1;                            //  OUTPUT analog - headset minijack

AudioOutputUSB           usb2;     

AudioSynthNoiseWhite      whitenoise;

AudioConnection          PatchCord0 (i2s0,0, usb2,1); // audio thru test
AudioConnection          PatchCord1 (whitenoise,0, usb2,0); // audio thru test


void setup()
{
  pinMode(LED_BUILTIN,OUTPUT);

  delay(10);  AudioMemory(25);  delay(50);  
  
  Serial.begin(115200);
  delay (500);                                     // Let the pc start up 
  Serial.print("setup() entered");

  // Enable the audio shield and set the output volume.
  sgtl5000_1.enable();
  delay(100);
  sgtl5000_1.inputSelect(AUDIO_INPUT_MIC);        // Analog mic element on audio shield
  sgtl5000_1.micGain(25);
  sgtl5000_1.volume(0.2);                         //headphone volume
  whitenoise.amplitude(0.5);


}

void loop()
{
  Serial.print("MEM:");Serial.println(AudioMemoryUsageMax() );
  delay(5000);
}