Found the solution, a newbie mistake, that’s all. Just had to start the flight from within the headset (the flight not MSFS) while I was starting the flight from the desktop and then putting my headset on. By coincidence this produced the same issue as starting MSFS from the desktop displayed within WMR.
While I’ve been a flight simmer for many years, I am very new to VR. Must have started MSFS successfully a dozen or more times in VR, but avoided this start procedure issue without being aware of it.
Thanks to those who replied.