Microphone does not create sound for other Zoom attendees.

I have a Lenovo E15. The built-in camera works fine, however no other Zoom attendee can hear me through the built-in microphone (Synaptics). Online tests of the microphone work perfectly, plays back with no issue. Other apps using the microphone work. Testing in Zoom shows the microphone sound bars going up and down while I speak, but there is no sound playing back. When I plug in a third-party microphone (it's a Yeti) the sound is picked up and plays for Zoom members perfectly. Any idea why my built-in Synaptics microphone refuses to work with Zoom, but works with everything else?  This microphone worked for months (system is less than a year old), but of late, this trouble.

Thank you. --drose