NAudio - WaveInEvent DataAvailable not firing

Question

My code is pretty simple - but the event never fires!

_msWaveInput = new()
{
    DeviceNumber = validDeviceNumber,
    WaveFormat = new NAudio.Wave.WaveFormat(rate: 48000, bits: 16, channels: 2),
    NumberOfBuffers = 1,
    BufferMilliseconds = bufferSizeMs
};

_msWaveInput.DataAvailable += WaveIn_DataAvailable;            
_msWaveInput?.StartRecording();

private void WaveIn_DataAvailable(object? sender, WaveInEventArgs e)
{
   // never fires!
}

If it's relevant, this is a console app ... :

  <PropertyGroup>
    <OutputType>Exe</OutputType>
    <TargetFramework>net6.0-windows</TargetFramework>
    <ImplicitUsings>enable</ImplicitUsings>
    <Nullable>enable</Nullable>
    <Platforms>AnyCPU;x64</Platforms>
  </PropertyGroup>

... with NAudio 2.1:

<PackageReference Include="NAudio" Version="2.1.0" />

The device numbers are made available with another simple piece of NAudio standard code:

for (int i = -1; i < NAudio.Wave.WaveIn.DeviceCount; i++)
{
    // i is the device number - I have tried them all!
}