Dear StevenK
Thank you very much for your prompt response.
I ran the Audio Troubleshooter, set the Headphone as default and am back to normal.
I do not understand why this has corrected the problem; but am happy that I can now use my earphones. Thank you.
Kind regards
JanieKaung
I think a recent update disabled headphone jack detection! It stopped switching automatically for me
Edit: I see a bunch of Realtek driver updates in recent history. That's the chip the sound device uses. I think it introduced a bug.