mac microphone not working right

Hi, I hope someone can help, I have tried everything I could find online! My MacBook is 2017 , recently updated. The microphone stopped working in the middle of a zoom meeting. It no longer works on

zoom,

voice memo recorder

settings.

Yet It works perfectly for

Siri,

dictation

online microphone checker.

I have done all the stuff that has been recommended. Updated, restarted, pram, checked that all the relevant settings are ticked. I am at a loss now and have no idea what is wrong. It would be easier to understand if it wasn't working at all, but it does. Siri can answer anything but tells me he can hear me ok when I ask him! ZOOM is important and it is getting embarrassing. Ny help would be very much appreciated.