If I understand the manual correctly this should appear as an A/D Input but I get nothing.

No, not at all. A VST running in the computer is in the digital domain. Only analog signal physically connected to the MOXF’s 1/4” inputs on the back panel is referred to as A/D Input.

The audio from the VSTi in the computer arrives in the MOXF (acting as audio interface) via the USB cable, passing through the DAW Level Slider on the MOXF front panel. This allows you set the volume of audio coming in from the computer.

We will assume you are using the Yamaha Steinberg USB Driver (when it is not mentioned it can mean only 2 things: it is being used or it is not being used. It needs to be used to properly handle MIDI and Audio with your computer).

Make sure the Audio Setup in your software is using the Yamaha Steinberg USB Driver and is set to the MOXF “MainL&R” as the Stereo Output.
Make sure you raise the DAW LEVEL slider to the appropriate listening level. It feeds computer audio to the MOXF’s Main Output which is controlled by the Main Volume Slider... which feeds your speakers.

As audio interface the MOXF is responsible for all audio entering and coming back out of the computer. The MOXF Main L&R Outputs must be connected to a quality sound system. The audio input takes in audio and routes audio out to the speakers. (The computer’s built-in sound system is replaced by the MOXF).

Let us know.

😀 😀 😀 It works! Many thanks for pointing me in the right direction. One slight peculiarity is that I have a choice of audio drivers, ASIO and WASAPI. Is there a preference?

ASIO - Audio Streaming Input Output is a standard protocol for getting audio into and back out of your computer in a timely fashion. Musicians are such sticklers about TIMING. Low Latency is necessary for music recording - especially for OVERDUB recording... where you are playing back some tracks while adding new tracks, simultaneously. Any significant delay in TIMING makes it impossible to play along.

The Yamaha Steinberg USB Driver is an ASIO Driver.