Issues with mono audio sidechain using tutorial from documentation, Mac OSX v 13.5.1, XCode v 14.3.1

I am attempting to code my first plugin using the tutorial from the documentation.
The plugin works as expected (although there is no GUI) until the portion where I try to add a mono audio sidechain. My code is as follows:
tresult PLUGIN_API TestProcessor::initialize (FUnknown* context)
//—always initialize the parent-------
tresult result = AudioEffect::initialize (context);
// if everything Ok, continue
if (result != kResultOk)
return result;


//---create Event In/Out busses (1 bus with only 1 channel)------
addEventInput (STR16 ("Event In"), 1);
// create a Mono SideChain input bus
addAudioInput (STR16 ("Mono Aux In"), Steinberg::Vst::SpeakerArr::kMono, Steinberg::Vst::kAux, 0);

return kResultOk;

I have made sure to include all the necessary header files, but the error I get is “Command PhaseScriptExecution failed with a nonzero exit code”. The TestSuite that it fails on is Single Precision (32 bit) Tests. Does anyone know what my issue is, or does it lie somewhere else in my code? Any guidance would be greatly appreciated.

your plugin should have a main audio input…
just do this
addAudioInput (STR16 (“Mono Aux In”), Steinberg::Vst::SpeakerArr::kMono);