I'm the OP, here is the final report and result.
My fingers were poking and pressing here and there in line with the various suggestions posted above when a notification flashed on to screen demanding to know the nature of the device that had been plugged in....(i.e. was my headset).
When this demand was satisfied, the laptop seemed to sense that the headset was there and now it's music to my ears. Of course this pleases me.
Thank you to all who posted to help.