I had similar issues with their macOS app using a pretty basic headphone+microphone setup (EarPods). I ended up leaving it off and not re-installing in on my latest setup.

I've had a subscription from mid-2019, though I no longer use it. I find Zoom's basic noise suppression good enough for calls.

Have you used the internal mic?

I found out that if the phone is too far away, the voice would flagged as ‚background chatting‘ and therefore muted.

Once I connected a headset those issues went away.