Android: wired earphones not working

I have wired earphones (without a built-in microphone) with an Android phone.  All sound in all Android applications went through earphones. In a Zoom meeting, however, earphones were neglected: the appl only allowed switching between and ear speaker and a loud speaker, as if no earphones were plugged in. it may be important that earphones are plugged via a 3.5/USB-C adapter. of course. I have tried to plug them out and back in several times, to no avail. How can I get Zoom to "see" and use my earphones? Thank you.