Internal mic not working on zoom

I am experiencing regular issues with my internal microphone not working on Zoom and Teams (though have only tried Teams once recently). I'm not muted on Zoom and sound settings seem correct. When I use my Zoom account on other devices it works fine. There is no issue with me hearing others or my video.

I've gone through all the sound settings on Mac and can't see any obvious issues. I read that switching dictation off and on can sometimes fix it. Tried this just before Zoom meetings and it fixed the problem the first three times but now stopped being effective too. Dictation works perfectly well, as does Siri, just not on Zoom and Teams.

Has anyone else experienced this and fixed this issue?