Thank you for your comments. I have tried the suggestion of monitoring the input directly, I had to search for monitoring on Windows 11 though.
Yes, I did get audio coming out of both loudspeakers on my laptop, but it was still only the left channel coming out of both speakers. I checked this by unplugging each RCA channel at the input to the sound grabber.
So… It looks as though the problem is either with the laptop/windows and what it does with the audio coming into the USB port, or…
It is the USB sound grabber itself.
However, I am more inclined to believe it is the laptop/Windows, because the Left signal is coming out of both loudspeakers. If it was the grabber, then I should get sound out of only one loudspeaker.
After yesterdays fruitless text chat with Windows Tech, where he checked my settings and said that it was not Windows, but the App (Audacity), I am now at a complete loss as to what to do next?
Any suggestions, please?